[PATCH 00/18] git notes merge

[PATCH 00/18] git notes merge

[Johan Herland]

Hi,

This is the 2nd iteration of the 'git notes merge' patch series.

Changes between the 1st WIP/RFC iteration and this version:

- Rebased on top of e93487d which obsoletes patch #7 in the previous
  series. AFAICS, it now merges cleanly against "master", and almost
  cleanly (modulo one trivial conflict) against "next". If desired,
  I can rebase the series onto "next" to avoid the trivial conflict.

- (Jonathan Nieder) Future-proof by always checking add_note() return
  value.

- (Stephen Boyd) Simplify argc logic.

- (Stephen Boyd) Use test_commit.

- (Stephen Boyd) Use "automatically resolves" instead of
  "auto-resolves".

- Renamed -X/--resolve to -s/--strategy. This is more in line with
  'git merge' (although the available strategies are different), and
  allows us to use -X for strategy-specific options in the future.

- Documentation: Moved documentation of notes merge strategies into
  its own section.

- Implemented manual conflict resolution of notes. Conflicting note
  entries are stored in .git/NOTES_MERGE_WORKTREE/*, while the
  non-conflicting note entries are committed, and referenced by
  .git/NOTES_MERGE_PARTIAL (aka. the partial merge result). When the
  conflicts have been edited/fixed, the user calls
  'git notes merge --commit' to recombine the partial merge result and
  the resolved conflicts to produce the final notes merge result.
  Alternatively, the user can call 'git notes merge --reset' to abort
  the notes merge.

- Add another auto-resolving notes merge strategy: "cat_sort_uniq"

- Test merging of notes trees at different fanout levels


To be done in later series:

- Handle merging of notes trees with non-notes

- Allow notes merge strategies to be specified (per (group of?) notes
  ref) in the config


Some open questions:

- Should we refuse to finalize a notes merge when conflict markers
  present in .git/NOTES_MERGE_WORKTREE? Since add/commit in regular
  merges does NOT do this, I have not implemented it for notes merge.

- When resolving notes merge conflicts, you can add/remove files/notes
  in .git/NOTES_MERGE_WORKTREE; 'git notes merge --commit' does not
  check that the notes have any relationship to the notes originally
  put there by 'git notes merge'. Should we warn about removed and
  added notes in .git/NOTES_MERGE_WORKTREE? Currently we don't, and
  I'm not sure it's worth it. Users can always review the merge commit
  afterwards.

- Fetching and pushing note refs:
  - Add refs/notes/* to default fetch refspec?
  - A way to specify (at clone time) which refspec(s) to set up?
  - A way for the remote repo to hint at which refspecs you might want
    to set up (by default?)


Have fun! :)

...Johan


Johan Herland (18):
  (trivial) notes.h: Minor documentation fixes to copy_notes()
  notes.h: Make default_notes_ref() available in notes API
  notes.h/c: Clarify the handling of notes objects that are == null_sha1
  notes.h/c: Propagate combine_notes_fn return value to add_note() and beyond
  (trivial) t3303: Indent with tabs instead of spaces for consistency
  notes.c: Use two newlines (instead of one) when concatenating notes
  builtin/notes.c: Split notes ref DWIMmery into a separate function
  git notes merge: Initial implementation handling trivial merges only
  builtin/notes.c: Refactor creation of notes commits.
  git notes merge: Handle real, non-conflicting notes merges
  git notes merge: Add automatic conflict resolvers (ours, theirs, union)
  Documentation: Preliminary docs on 'git notes merge'
  git notes merge: Manual conflict resolution, part 1/2
  git notes merge: Manual conflict resolution, part 2/2
  git notes merge: List conflicting notes in notes merge commit message
  git notes merge: --commit should fail if underlying notes ref has moved
  git notes merge: Add another auto-resolving strategy: "cat_sort_uniq"
  git notes merge: Add testcases for merging notes trees at different fanouts

 Documentation/git-notes.txt           |   81 ++++-
 Makefile                              |    2 +
 builtin.h                             |    2 +-
 builtin/notes.c                       |  245 ++++++++++--
 notes-cache.c                         |    3 +-
 notes-merge.c                         |  718 +++++++++++++++++++++++++++++++++
 notes-merge.h                         |   92 +++++
 notes.c                               |  272 +++++++++-----
 notes.h                               |   47 ++-
 t/t3301-notes.sh                      |    4 +
 t/t3303-notes-subtrees.sh             |   19 +-
 t/t3308-notes-merge.sh                |  327 +++++++++++++++
 t/t3309-notes-merge-auto-resolve.sh   |  647 +++++++++++++++++++++++++++++
 t/t3310-notes-merge-manual-resolve.sh |  556 +++++++++++++++++++++++++
 t/t3311-notes-merge-fanout.sh         |  436 ++++++++++++++++++++
 t/t3404-rebase-interactive.sh         |    1 +
 t/t9301-fast-import-notes.sh          |    5 +
 17 files changed, 3315 insertions(+), 142 deletions(-)
 create mode 100644 notes-merge.c
 create mode 100644 notes-merge.h
 create mode 100755 t/t3308-notes-merge.sh
 create mode 100755 t/t3309-notes-merge-auto-resolve.sh
 create mode 100755 t/t3310-notes-merge-manual-resolve.sh
 create mode 100755 t/t3311-notes-merge-fanout.sh

--
1.7.3.98.g5ad7d9

[PATCH 01/18] (trivial) notes.h: Minor documentation fixes to copy_notes()

[Johan Herland]

Signed-off-by: Johan Herland <johan@herland.net>
---
 notes.h |    5 +++++
 1 files changed, 5 insertions(+), 0 deletions(-)

diff --git a/notes.h b/notes.h
index 65fc3a6..c0288b0 100644
--- a/notes.h
+++ b/notes.h
@@ -104,6 +104,10 @@ const unsigned char *get_note(struct notes_tree *t,
  * Copy a note from one object to another in the given notes_tree.
  *
  * Fails if the to_obj already has a note unless 'force' is true.
+ *
+ * IMPORTANT: The changes made by copy_note() to the given notes_tree structure
+ * are not persistent until a subsequent call to write_notes_tree() returns
+ * zero.
  */
 int copy_note(struct notes_tree *t,
 	      const unsigned char *from_obj, const unsigned char *to_obj,
@@ -149,6 +153,7 @@ int copy_note(struct notes_tree *t,
  * notes tree) from within the callback:
  * - add_note()
  * - remove_note()
+ * - copy_note()
  * - free_notes()
  */
 typedef int each_note_fn(const unsigned char *object_sha1,
-- 
1.7.3.98.g5ad7d9

[PATCH 02/18] notes.h: Make default_notes_ref() available in notes API

[Johan Herland]

Signed-off-by: Johan Herland <johan@herland.net>
---
 notes.c |    2 +-
 notes.h |   14 ++++++++++++++
 2 files changed, 15 insertions(+), 1 deletions(-)

diff --git a/notes.c b/notes.c
index 1978244..79fd850 100644
--- a/notes.c
+++ b/notes.c
@@ -898,7 +898,7 @@ static int notes_display_config(const char *k, const char *v, void *cb)
 	return 0;
 }
 
-static const char *default_notes_ref(void)
+const char *default_notes_ref(void)
 {
 	const char *notes_ref = NULL;
 	if (!notes_ref)
diff --git a/notes.h b/notes.h
index c0288b0..20db42f 100644
--- a/notes.h
+++ b/notes.h
@@ -44,6 +44,20 @@ extern struct notes_tree {
 } default_notes_tree;
 
 /*
+ * Return the default notes ref.
+ *
+ * The default notes ref is the notes ref that is used when notes_ref == NULL
+ * is passed to init_notes().
+ *
+ * This the first of the following to be defined:
+ * 1. The '--ref' option to 'git notes', if given
+ * 2. The $GIT_NOTES_REF environment variable, if set
+ * 3. The value of the core.notesRef config variable, if set
+ * 4. GIT_NOTES_DEFAULT_REF (i.e. "refs/notes/commits")
+ */
+const char *default_notes_ref(void);
+
+/*
  * Flags controlling behaviour of notes tree initialization
  *
  * Default behaviour is to initialize the notes tree from the tree object
-- 
1.7.3.98.g5ad7d9

[PATCH 03/18] notes.h/c: Clarify the handling of notes objects that are == null_sha1

[Johan Herland]

Clearly specify how combine_notes functions are expected to handle null_sha1
in input, and how they may set the result to null_sha1 in order to cause
the removal of a note.

Also document that passing note_sha1 == null_sha1 to add_note() is usually
a no-op, except in cases where combining it with an existing note yields a
new/changed result.

The only functional changes in this patch concern the handling of null_sha1
in notes_tree_insert(). Otherwise the patch consists solely of reordering
functions in notes.c to avoid use-before-declaration, and adding
documentation to notes.h.

Signed-off-by: Johan Herland <johan@herland.net>
---
 notes.c |  158 +++++++++++++++++++++++++++++++++-----------------------------
 notes.h |   16 ++++++-
 2 files changed, 99 insertions(+), 75 deletions(-)

diff --git a/notes.c b/notes.c
index 79fd850..9e92021 100644
--- a/notes.c
+++ b/notes.c
@@ -150,6 +150,79 @@ static struct leaf_node *note_tree_find(struct notes_tree *t,
 }
 
 /*
+ * How to consolidate an int_node:
+ * If there are > 1 non-NULL entries, give up and return non-zero.
+ * Otherwise replace the int_node at the given index in the given parent node
+ * with the only entry (or a NULL entry if no entries) from the given tree,
+ * and return 0.
+ */
+static int note_tree_consolidate(struct int_node *tree,
+	struct int_node *parent, unsigned char index)
+{
+	unsigned int i;
+	void *p = NULL;
+
+	assert(tree && parent);
+	assert(CLR_PTR_TYPE(parent->a[index]) == tree);
+
+	for (i = 0; i < 16; i++) {
+		if (GET_PTR_TYPE(tree->a[i]) != PTR_TYPE_NULL) {
+			if (p) /* more than one entry */
+				return -2;
+			p = tree->a[i];
+		}
+	}
+
+	/* replace tree with p in parent[index] */
+	parent->a[index] = p;
+	free(tree);
+	return 0;
+}
+
+/*
+ * To remove a leaf_node:
+ * Search to the tree location appropriate for the given leaf_node's key:
+ * - If location does not hold a matching entry, abort and do nothing.
+ * - Replace the matching leaf_node with a NULL entry (and free the leaf_node).
+ * - Consolidate int_nodes repeatedly, while walking up the tree towards root.
+ */
+static void note_tree_remove(struct notes_tree *t, struct int_node *tree,
+		unsigned char n, struct leaf_node *entry)
+{
+	struct leaf_node *l;
+	struct int_node *parent_stack[20];
+	unsigned char i, j;
+	void **p = note_tree_search(t, &tree, &n, entry->key_sha1);
+
+	assert(GET_PTR_TYPE(entry) == 0); /* no type bits set */
+	if (GET_PTR_TYPE(*p) != PTR_TYPE_NOTE)
+		return; /* type mismatch, nothing to remove */
+	l = (struct leaf_node *) CLR_PTR_TYPE(*p);
+	if (hashcmp(l->key_sha1, entry->key_sha1))
+		return; /* key mismatch, nothing to remove */
+
+	/* we have found a matching entry */
+	free(l);
+	*p = SET_PTR_TYPE(NULL, PTR_TYPE_NULL);
+
+	/* consolidate this tree level, and parent levels, if possible */
+	if (!n)
+		return; /* cannot consolidate top level */
+	/* first, build stack of ancestors between root and current node */
+	parent_stack[0] = t->root;
+	for (i = 0; i < n; i++) {
+		j = GET_NIBBLE(i, entry->key_sha1);
+		parent_stack[i + 1] = CLR_PTR_TYPE(parent_stack[i]->a[j]);
+	}
+	assert(i == n && parent_stack[i] == tree);
+	/* next, unwind stack until note_tree_consolidate() is done */
+	while (i > 0 &&
+	       !note_tree_consolidate(parent_stack[i], parent_stack[i - 1],
+				      GET_NIBBLE(i - 1, entry->key_sha1)))
+		i--;
+}
+
+/*
  * To insert a leaf_node:
  * Search to the tree location appropriate for the given leaf_node's key:
  * - If location is unused (NULL), store the tweaked pointer directly there
@@ -175,7 +248,10 @@ static void note_tree_insert(struct notes_tree *t, struct int_node *tree,
 	switch (GET_PTR_TYPE(*p)) {
 	case PTR_TYPE_NULL:
 		assert(!*p);
-		*p = SET_PTR_TYPE(entry, type);
+		if (is_null_sha1(entry->val_sha1))
+			free(entry);
+		else
+			*p = SET_PTR_TYPE(entry, type);
 		return;
 	case PTR_TYPE_NOTE:
 		switch (type) {
@@ -191,6 +267,9 @@ static void note_tree_insert(struct notes_tree *t, struct int_node *tree,
 					    sha1_to_hex(l->val_sha1),
 					    sha1_to_hex(entry->val_sha1),
 					    sha1_to_hex(l->key_sha1));
+
+				if (is_null_sha1(l->val_sha1))
+					note_tree_remove(t, tree, n, entry);
 				free(entry);
 				return;
 			}
@@ -222,6 +301,10 @@ static void note_tree_insert(struct notes_tree *t, struct int_node *tree,
 	/* non-matching leaf_node */
 	assert(GET_PTR_TYPE(*p) == PTR_TYPE_NOTE ||
 	       GET_PTR_TYPE(*p) == PTR_TYPE_SUBTREE);
+	if (is_null_sha1(entry->val_sha1)) { /* skip insertion of empty note */
+		free(entry);
+		return;
+	}
 	new_node = (struct int_node *) xcalloc(sizeof(struct int_node), 1);
 	note_tree_insert(t, new_node, n + 1, l, GET_PTR_TYPE(*p),
 			 combine_notes);
@@ -229,79 +312,6 @@ static void note_tree_insert(struct notes_tree *t, struct int_node *tree,
 	note_tree_insert(t, new_node, n + 1, entry, type, combine_notes);
 }
 
-/*
- * How to consolidate an int_node:
- * If there are > 1 non-NULL entries, give up and return non-zero.
- * Otherwise replace the int_node at the given index in the given parent node
- * with the only entry (or a NULL entry if no entries) from the given tree,
- * and return 0.
- */
-static int note_tree_consolidate(struct int_node *tree,
-	struct int_node *parent, unsigned char index)
-{
-	unsigned int i;
-	void *p = NULL;
-
-	assert(tree && parent);
-	assert(CLR_PTR_TYPE(parent->a[index]) == tree);
-
-	for (i = 0; i < 16; i++) {
-		if (GET_PTR_TYPE(tree->a[i]) != PTR_TYPE_NULL) {
-			if (p) /* more than one entry */
-				return -2;
-			p = tree->a[i];
-		}
-	}
-
-	/* replace tree with p in parent[index] */
-	parent->a[index] = p;
-	free(tree);
-	return 0;
-}
-
-/*
- * To remove a leaf_node:
- * Search to the tree location appropriate for the given leaf_node's key:
- * - If location does not hold a matching entry, abort and do nothing.
- * - Replace the matching leaf_node with a NULL entry (and free the leaf_node).
- * - Consolidate int_nodes repeatedly, while walking up the tree towards root.
- */
-static void note_tree_remove(struct notes_tree *t, struct int_node *tree,
-		unsigned char n, struct leaf_node *entry)
-{
-	struct leaf_node *l;
-	struct int_node *parent_stack[20];
-	unsigned char i, j;
-	void **p = note_tree_search(t, &tree, &n, entry->key_sha1);
-
-	assert(GET_PTR_TYPE(entry) == 0); /* no type bits set */
-	if (GET_PTR_TYPE(*p) != PTR_TYPE_NOTE)
-		return; /* type mismatch, nothing to remove */
-	l = (struct leaf_node *) CLR_PTR_TYPE(*p);
-	if (hashcmp(l->key_sha1, entry->key_sha1))
-		return; /* key mismatch, nothing to remove */
-
-	/* we have found a matching entry */
-	free(l);
-	*p = SET_PTR_TYPE(NULL, PTR_TYPE_NULL);
-
-	/* consolidate this tree level, and parent levels, if possible */
-	if (!n)
-		return; /* cannot consolidate top level */
-	/* first, build stack of ancestors between root and current node */
-	parent_stack[0] = t->root;
-	for (i = 0; i < n; i++) {
-		j = GET_NIBBLE(i, entry->key_sha1);
-		parent_stack[i + 1] = CLR_PTR_TYPE(parent_stack[i]->a[j]);
-	}
-	assert(i == n && parent_stack[i] == tree);
-	/* next, unwind stack until note_tree_consolidate() is done */
-	while (i > 0 &&
-	       !note_tree_consolidate(parent_stack[i], parent_stack[i - 1],
-				      GET_NIBBLE(i - 1, entry->key_sha1)))
-		i--;
-}
-
 /* Free the entire notes data contained in the given tree */
 static void note_tree_free(struct int_node *tree)
 {
diff --git a/notes.h b/notes.h
index 20db42f..79ea797 100644
--- a/notes.h
+++ b/notes.h
@@ -12,7 +12,10 @@
  * resulting SHA1 into the first SHA1 argument (cur_sha1). A non-zero return
  * value indicates failure.
  *
- * The two given SHA1s must both be non-NULL and different from each other.
+ * The two given SHA1s shall both be non-NULL and different from each other.
+ * Either of them (but not both) may be == null_sha1, which indicates an
+ * empty/non-existent note. If the resulting SHA1 (cur_sha1) is == null_sha1,
+ * the note will be removed from the notes tree.
  *
  * The default combine_notes function (you get this when passing NULL) is
  * combine_notes_concatenate(), which appends the contents of the new note to
@@ -90,6 +93,17 @@ void init_notes(struct notes_tree *t, const char *notes_ref,
 /*
  * Add the given note object to the given notes_tree structure
  *
+ * If there already exists a note for the given object_sha1, the given
+ * combine_notes function is invoked to break the tie. If not given (i.e.
+ * combine_notes == NULL), the default combine_notes function for the given
+ * notes_tree is used.
+ *
+ * Passing note_sha1 == null_sha1 indicates the addition of an
+ * empty/non-existent note. This is a (potentially expensive) no-op unless
+ * there already exists a note for the given object_sha1, AND combining that
+ * note with the empty note (using the given combine_notes function) results
+ * in a new/changed note.
+ *
  * IMPORTANT: The changes made by add_note() to the given notes_tree structure
  * are not persistent until a subsequent call to write_notes_tree() returns
  * zero.
-- 
1.7.3.98.g5ad7d9

[PATCH 04/18] notes.h/c: Propagate combine_notes_fn return value to add_note() and beyond

[Johan Herland]

The combine_notes_fn functions uses a non-zero return value to indicate
failure. However, this return value was converted to a call to die()
in note_tree_insert().

Instead, propagate this return value out to add_note(), and return it
from there to enable the caller to handle errors appropriately.

This patch has been improved by the following contributions:
- Jonathan Nieder: Future-proof by always checking add_note() return value

Cc: Jonathan Nieder <jrnieder@gmail.com>
Signed-off-by: Johan Herland <johan@herland.net>
---
 builtin/notes.c |   11 +++++----
 notes-cache.c   |    3 +-
 notes.c         |   59 ++++++++++++++++++++++++++++--------------------------
 notes.h         |   11 +++++++--
 4 files changed, 46 insertions(+), 38 deletions(-)

diff --git a/builtin/notes.c b/builtin/notes.c
index fbc347c..35f6eb6 100644
--- a/builtin/notes.c
+++ b/builtin/notes.c
@@ -573,8 +573,8 @@ static int add(int argc, const char **argv, const char *prefix)
 
 	if (is_null_sha1(new_note))
 		remove_note(t, object);
-	else
-		add_note(t, object, new_note, combine_notes_overwrite);
+	else if (add_note(t, object, new_note, combine_notes_overwrite))
+		die("confused: combine_notes_overwrite failed");
 
 	snprintf(logmsg, sizeof(logmsg), "Notes %s by 'git notes %s'",
 		 is_null_sha1(new_note) ? "removed" : "added", "add");
@@ -653,7 +653,8 @@ static int copy(int argc, const char **argv, const char *prefix)
 		goto out;
 	}
 
-	add_note(t, object, from_note, combine_notes_overwrite);
+	if (add_note(t, object, from_note, combine_notes_overwrite))
+		die("confused: combine_notes_overwrite failed");
 	commit_notes(t, "Notes added by 'git notes copy'");
 out:
 	free_notes(t);
@@ -712,8 +713,8 @@ static int append_edit(int argc, const char **argv, const char *prefix)
 
 	if (is_null_sha1(new_note))
 		remove_note(t, object);
-	else
-		add_note(t, object, new_note, combine_notes_overwrite);
+	else if (add_note(t, object, new_note, combine_notes_overwrite))
+		die("confused: combine_notes_overwrite failed");
 
 	snprintf(logmsg, sizeof(logmsg), "Notes %s by 'git notes %s'",
 		 is_null_sha1(new_note) ? "removed" : "added", argv[0]);
diff --git a/notes-cache.c b/notes-cache.c
index dee6d62..4c8984e 100644
--- a/notes-cache.c
+++ b/notes-cache.c
@@ -89,6 +89,5 @@ int notes_cache_put(struct notes_cache *c, unsigned char key_sha1[20],
 
 	if (write_sha1_file(data, size, "blob", value_sha1) < 0)
 		return -1;
-	add_note(&c->tree, key_sha1, value_sha1, NULL);
-	return 0;
+	return add_note(&c->tree, key_sha1, value_sha1, NULL);
 }
diff --git a/notes.c b/notes.c
index 9e92021..4f3d094 100644
--- a/notes.c
+++ b/notes.c
@@ -235,13 +235,14 @@ static void note_tree_remove(struct notes_tree *t, struct int_node *tree,
  * - Else, create a new int_node, holding both the node-at-location and the
  *   node-to-be-inserted, and store the new int_node into the location.
  */
-static void note_tree_insert(struct notes_tree *t, struct int_node *tree,
+static int note_tree_insert(struct notes_tree *t, struct int_node *tree,
 		unsigned char n, struct leaf_node *entry, unsigned char type,
 		combine_notes_fn combine_notes)
 {
 	struct int_node *new_node;
 	struct leaf_node *l;
 	void **p = note_tree_search(t, &tree, &n, entry->key_sha1);
+	int ret = 0;
 
 	assert(GET_PTR_TYPE(entry) == 0); /* no type bits set */
 	l = (struct leaf_node *) CLR_PTR_TYPE(*p);
@@ -252,26 +253,21 @@ static void note_tree_insert(struct notes_tree *t, struct int_node *tree,
 			free(entry);
 		else
 			*p = SET_PTR_TYPE(entry, type);
-		return;
+		return 0;
 	case PTR_TYPE_NOTE:
 		switch (type) {
 		case PTR_TYPE_NOTE:
 			if (!hashcmp(l->key_sha1, entry->key_sha1)) {
 				/* skip concatenation if l == entry */
 				if (!hashcmp(l->val_sha1, entry->val_sha1))
-					return;
+					return 0;
 
-				if (combine_notes(l->val_sha1, entry->val_sha1))
-					die("failed to combine notes %s and %s"
-					    " for object %s",
-					    sha1_to_hex(l->val_sha1),
-					    sha1_to_hex(entry->val_sha1),
-					    sha1_to_hex(l->key_sha1));
-
-				if (is_null_sha1(l->val_sha1))
+				ret = combine_notes(l->val_sha1,
+						    entry->val_sha1);
+				if (!ret && is_null_sha1(l->val_sha1))
 					note_tree_remove(t, tree, n, entry);
 				free(entry);
-				return;
+				return ret;
 			}
 			break;
 		case PTR_TYPE_SUBTREE:
@@ -280,7 +276,7 @@ static void note_tree_insert(struct notes_tree *t, struct int_node *tree,
 				/* unpack 'entry' */
 				load_subtree(t, entry, tree, n);
 				free(entry);
-				return;
+				return 0;
 			}
 			break;
 		}
@@ -291,9 +287,8 @@ static void note_tree_insert(struct notes_tree *t, struct int_node *tree,
 			*p = NULL;
 			load_subtree(t, l, tree, n);
 			free(l);
-			note_tree_insert(t, tree, n, entry, type,
-					 combine_notes);
-			return;
+			return note_tree_insert(t, tree, n, entry, type,
+						combine_notes);
 		}
 		break;
 	}
@@ -303,13 +298,17 @@ static void note_tree_insert(struct notes_tree *t, struct int_node *tree,
 	       GET_PTR_TYPE(*p) == PTR_TYPE_SUBTREE);
 	if (is_null_sha1(entry->val_sha1)) { /* skip insertion of empty note */
 		free(entry);
-		return;
+		return 0;
 	}
 	new_node = (struct int_node *) xcalloc(sizeof(struct int_node), 1);
-	note_tree_insert(t, new_node, n + 1, l, GET_PTR_TYPE(*p),
-			 combine_notes);
-	*p = SET_PTR_TYPE(new_node, PTR_TYPE_INTERNAL);
-	note_tree_insert(t, new_node, n + 1, entry, type, combine_notes);
+	ret = note_tree_insert(t, new_node, n + 1, l, GET_PTR_TYPE(*p),
+			       combine_notes);
+	if (!ret) {
+		*p = SET_PTR_TYPE(new_node, PTR_TYPE_INTERNAL);
+		ret = note_tree_insert(t, new_node, n + 1, entry, type,
+				       combine_notes);
+	}
+	return ret;
 }
 
 /* Free the entire notes data contained in the given tree */
@@ -452,8 +451,12 @@ static void load_subtree(struct notes_tree *t, struct leaf_node *subtree,
 				l->key_sha1[19] = (unsigned char) len;
 				type = PTR_TYPE_SUBTREE;
 			}
-			note_tree_insert(t, node, n, l, type,
-					 combine_notes_concatenate);
+			if (note_tree_insert(t, node, n, l, type,
+					     combine_notes_concatenate))
+				die("Failed to load %s %s into notes tree "
+				    "from %s",
+				    type == PTR_TYPE_NOTE ? "note" : "subtree",
+				    sha1_to_hex(l->key_sha1), t->ref);
 		}
 		continue;
 
@@ -1014,7 +1017,7 @@ void init_display_notes(struct display_notes_opt *opt)
 	string_list_clear(&display_notes_refs, 0);
 }
 
-void add_note(struct notes_tree *t, const unsigned char *object_sha1,
+int add_note(struct notes_tree *t, const unsigned char *object_sha1,
 		const unsigned char *note_sha1, combine_notes_fn combine_notes)
 {
 	struct leaf_node *l;
@@ -1028,7 +1031,7 @@ void add_note(struct notes_tree *t, const unsigned char *object_sha1,
 	l = (struct leaf_node *) xmalloc(sizeof(struct leaf_node));
 	hashcpy(l->key_sha1, object_sha1);
 	hashcpy(l->val_sha1, note_sha1);
-	note_tree_insert(t, t->root, 0, l, PTR_TYPE_NOTE, combine_notes);
+	return note_tree_insert(t, t->root, 0, l, PTR_TYPE_NOTE, combine_notes);
 }
 
 void remove_note(struct notes_tree *t, const unsigned char *object_sha1)
@@ -1204,7 +1207,7 @@ void format_display_notes(const unsigned char *object_sha1,
 
 int copy_note(struct notes_tree *t,
 	      const unsigned char *from_obj, const unsigned char *to_obj,
-	      int force, combine_notes_fn combine_fn)
+	      int force, combine_notes_fn combine_notes)
 {
 	const unsigned char *note = get_note(t, from_obj);
 	const unsigned char *existing_note = get_note(t, to_obj);
@@ -1213,9 +1216,9 @@ int copy_note(struct notes_tree *t,
 		return 1;
 
 	if (note)
-		add_note(t, to_obj, note, combine_fn);
+		return add_note(t, to_obj, note, combine_notes);
 	else if (existing_note)
-		add_note(t, to_obj, null_sha1, combine_fn);
+		return add_note(t, to_obj, null_sha1, combine_notes);
 
 	return 0;
 }
diff --git a/notes.h b/notes.h
index 79ea797..b372575 100644
--- a/notes.h
+++ b/notes.h
@@ -104,11 +104,13 @@ void init_notes(struct notes_tree *t, const char *notes_ref,
  * note with the empty note (using the given combine_notes function) results
  * in a new/changed note.
  *
+ * Returns zero on success; non-zero means combine_notes failed.
+ *
  * IMPORTANT: The changes made by add_note() to the given notes_tree structure
  * are not persistent until a subsequent call to write_notes_tree() returns
  * zero.
  */
-void add_note(struct notes_tree *t, const unsigned char *object_sha1,
+int add_note(struct notes_tree *t, const unsigned char *object_sha1,
 		const unsigned char *note_sha1, combine_notes_fn combine_notes);
 
 /*
@@ -131,7 +133,10 @@ const unsigned char *get_note(struct notes_tree *t,
 /*
  * Copy a note from one object to another in the given notes_tree.
  *
- * Fails if the to_obj already has a note unless 'force' is true.
+ * Returns 1 if the to_obj already has a note and 'force' is false. Otherwise,
+ * returns non-zero if 'force' is true, but the given combine_notes function
+ * failed to combine from_obj's note with to_obj's existing note.
+ * Returns zero on success.
  *
  * IMPORTANT: The changes made by copy_note() to the given notes_tree structure
  * are not persistent until a subsequent call to write_notes_tree() returns
@@ -139,7 +144,7 @@ const unsigned char *get_note(struct notes_tree *t,
  */
 int copy_note(struct notes_tree *t,
 	      const unsigned char *from_obj, const unsigned char *to_obj,
-	      int force, combine_notes_fn combine_fn);
+	      int force, combine_notes_fn combine_notes);
 
 /*
  * Flags controlling behaviour of for_each_note()
-- 
1.7.3.98.g5ad7d9

[PATCH 05/18] (trivial) t3303: Indent with tabs instead of spaces for consistency

[Johan Herland]

The rest of the file uses tabs for indenting. Fix the one function
that doesn't.

Signed-off-by: Johan Herland <johan@herland.net>
---
 t/t3303-notes-subtrees.sh |   18 +++++++++---------
 1 files changed, 9 insertions(+), 9 deletions(-)

diff --git a/t/t3303-notes-subtrees.sh b/t/t3303-notes-subtrees.sh
index 75ec187..d571708 100755
--- a/t/t3303-notes-subtrees.sh
+++ b/t/t3303-notes-subtrees.sh
@@ -168,15 +168,15 @@ INPUT_END
 }
 
 verify_concatenated_notes () {
-    git log | grep "^    " > output &&
-    i=$number_of_commits &&
-    while [ $i -gt 0 ]; do
-        echo "    commit #$i" &&
-        echo "    first note for commit #$i" &&
-        echo "    second note for commit #$i" &&
-        i=$(($i-1));
-    done > expect &&
-    test_cmp expect output
+	git log | grep "^    " > output &&
+	i=$number_of_commits &&
+	while [ $i -gt 0 ]; do
+		echo "    commit #$i" &&
+		echo "    first note for commit #$i" &&
+		echo "    second note for commit #$i" &&
+		i=$(($i-1));
+	done > expect &&
+	test_cmp expect output
 }
 
 test_expect_success 'test notes in no fanout concatenated with 2/38-fanout' 'test_concatenated_notes "s|^..|&/|" ""'
-- 
1.7.3.98.g5ad7d9

[PATCH 06/18] notes.c: Use two newlines (instead of one) when concatenating notes

[Johan Herland]

When using combine_notes_concatenate() to concatenate notes, it currently
ensures exactly one newline character between the given notes. However,
when using builtin/notes.c:create_note() to concatenate notes (e.g. by
'git notes append'), it adds a newline character to the trailing newline
of the preceding notes object, thus resulting in _two_ newlines (aka. a
blank line) separating contents of the two notes.

This patch brings combine_notes_concatenate() into consistency with
builtin/notes.c:create_note(), by ensuring exactly _two_ newline characters
between concatenated notes.

The patch also changes a few notes-related selftests accordingly.

Signed-off-by: Johan Herland <johan@herland.net>
---
 notes.c                       |    7 ++++---
 t/t3301-notes.sh              |    4 ++++
 t/t3303-notes-subtrees.sh     |    1 +
 t/t3404-rebase-interactive.sh |    1 +
 t/t9301-fast-import-notes.sh  |    5 +++++
 5 files changed, 15 insertions(+), 3 deletions(-)

diff --git a/notes.c b/notes.c
index 4f3d094..28afe2c 100644
--- a/notes.c
+++ b/notes.c
@@ -814,16 +814,17 @@ int combine_notes_concatenate(unsigned char *cur_sha1,
 		return 0;
 	}
 
-	/* we will separate the notes by a newline anyway */
+	/* we will separate the notes by two newlines anyway */
 	if (cur_msg[cur_len - 1] == '\n')
 		cur_len--;
 
 	/* concatenate cur_msg and new_msg into buf */
-	buf_len = cur_len + 1 + new_len;
+	buf_len = cur_len + 2 + new_len;
 	buf = (char *) xmalloc(buf_len);
 	memcpy(buf, cur_msg, cur_len);
 	buf[cur_len] = '\n';
-	memcpy(buf + cur_len + 1, new_msg, new_len);
+	buf[cur_len + 1] = '\n';
+	memcpy(buf + cur_len + 2, new_msg, new_len);
 	free(cur_msg);
 	free(new_msg);
 
diff --git a/t/t3301-notes.sh b/t/t3301-notes.sh
index 1d82f79..4bf4e52 100755
--- a/t/t3301-notes.sh
+++ b/t/t3301-notes.sh
@@ -955,6 +955,7 @@ Date:   Thu Apr 7 15:27:13 2005 -0700
 
 Notes (other):
     a fresh note
+$whitespace
     another fresh note
 EOF
 
@@ -976,8 +977,11 @@ Date:   Thu Apr 7 15:27:13 2005 -0700
 
 Notes (other):
     a fresh note
+$whitespace
     another fresh note
+$whitespace
     append 1
+$whitespace
     append 2
 EOF
 
diff --git a/t/t3303-notes-subtrees.sh b/t/t3303-notes-subtrees.sh
index d571708..704aee8 100755
--- a/t/t3303-notes-subtrees.sh
+++ b/t/t3303-notes-subtrees.sh
@@ -173,6 +173,7 @@ verify_concatenated_notes () {
 	while [ $i -gt 0 ]; do
 		echo "    commit #$i" &&
 		echo "    first note for commit #$i" &&
+		echo "    " &&
 		echo "    second note for commit #$i" &&
 		i=$(($i-1));
 	done > expect &&
diff --git a/t/t3404-rebase-interactive.sh b/t/t3404-rebase-interactive.sh
index 9f03ce6..9ed70dc 100755
--- a/t/t3404-rebase-interactive.sh
+++ b/t/t3404-rebase-interactive.sh
@@ -593,6 +593,7 @@ test_expect_success 'rebase -i can copy notes' '
 
 cat >expect <<EOF
 an earlier note
+
 a note
 EOF
 
diff --git a/t/t9301-fast-import-notes.sh b/t/t9301-fast-import-notes.sh
index a5c99d8..7cf8cd8 100755
--- a/t/t9301-fast-import-notes.sh
+++ b/t/t9301-fast-import-notes.sh
@@ -255,13 +255,18 @@ EOF
 
 INPUT_END
 
+whitespace="    "
+
 cat >expect <<EXPECT_END
     fourth commit
     pre-prefix of note for fourth commit
+$whitespace
     prefix of note for fourth commit
+$whitespace
     third note for fourth commit
     third commit
     prefix of note for third commit
+$whitespace
     third note for third commit
     second commit
     third note for second commit
-- 
1.7.3.98.g5ad7d9

[PATCH 07/18] builtin/notes.c: Split notes ref DWIMmery into a separate function

[Johan Herland]

expand_notes_ref() is a new function that performs the DWIM transformation
of "foo" -> "refs/notes/foo" where notes refs are expected.

This is done in preparation for future patches which will also need this
DWIM functionality.

Signed-off-by: Johan Herland <johan@herland.net>
---
 builtin/notes.c |   17 +++++++++++------
 1 files changed, 11 insertions(+), 6 deletions(-)

diff --git a/builtin/notes.c b/builtin/notes.c
index 35f6eb6..9c91c59 100644
--- a/builtin/notes.c
+++ b/builtin/notes.c
@@ -83,6 +83,16 @@ struct msg_arg {
 	struct strbuf buf;
 };
 
+static void expand_notes_ref(struct strbuf *sb)
+{
+	if (!prefixcmp(sb->buf, "refs/notes/"))
+		return; /* we're happy */
+	else if (!prefixcmp(sb->buf, "notes/"))
+		strbuf_insert(sb, 0, "refs/", 5);
+	else
+		strbuf_insert(sb, 0, "refs/notes/", 11);
+}
+
 static int list_each_note(const unsigned char *object_sha1,
 		const unsigned char *note_sha1, char *note_path,
 		void *cb_data)
@@ -839,13 +849,8 @@ int cmd_notes(int argc, const char **argv, const char *prefix)
 
 	if (override_notes_ref) {
 		struct strbuf sb = STRBUF_INIT;
-		if (!prefixcmp(override_notes_ref, "refs/notes/"))
-			/* we're happy */;
-		else if (!prefixcmp(override_notes_ref, "notes/"))
-			strbuf_addstr(&sb, "refs/");
-		else
-			strbuf_addstr(&sb, "refs/notes/");
 		strbuf_addstr(&sb, override_notes_ref);
+		expand_notes_ref(&sb);
 		setenv("GIT_NOTES_REF", sb.buf, 1);
 		strbuf_release(&sb);
 	}
-- 
1.7.3.98.g5ad7d9

[PATCH 08/18] git notes merge: Initial implementation handling trivial merges only

[Johan Herland]

This initial implementation of 'git notes merge' only handles the trivial
merge cases (i.e. where the merge is either a no-op, or a fast-forward).

The patch includes testcases for these trivial merge cases.

Future patches will extend the functionality of 'git notes merge'.

This patch has been improved by the following contributions:
- Stephen Boyd: Simplify argc logic
- Stephen Boyd: Use test_commit

Cc: Stephen Boyd <bebarino@gmail.com>
Signed-off-by: Johan Herland <johan@herland.net>
---
 Makefile               |    2 +
 builtin/notes.c        |   53 ++++++++++++++++++
 notes-merge.c          |  103 +++++++++++++++++++++++++++++++++++
 notes-merge.h          |   30 ++++++++++
 t/t3308-notes-merge.sh |  139 ++++++++++++++++++++++++++++++++++++++++++++++++
 5 files changed, 327 insertions(+), 0 deletions(-)
 create mode 100644 notes-merge.c
 create mode 100644 notes-merge.h
 create mode 100755 t/t3308-notes-merge.sh

diff --git a/Makefile b/Makefile
index f33648d..14c0ff1 100644
--- a/Makefile
+++ b/Makefile
@@ -503,6 +503,7 @@ LIB_H += mailmap.h
 LIB_H += merge-recursive.h
 LIB_H += notes.h
 LIB_H += notes-cache.h
+LIB_H += notes-merge.h
 LIB_H += object.h
 LIB_H += pack.h
 LIB_H += pack-refs.h
@@ -593,6 +594,7 @@ LIB_OBJS += merge-recursive.o
 LIB_OBJS += name-hash.o
 LIB_OBJS += notes.o
 LIB_OBJS += notes-cache.o
+LIB_OBJS += notes-merge.o
 LIB_OBJS += object.o
 LIB_OBJS += pack-check.o
 LIB_OBJS += pack-refs.o
diff --git a/builtin/notes.c b/builtin/notes.c
index 9c91c59..ec1d042 100644
--- a/builtin/notes.c
+++ b/builtin/notes.c
@@ -17,6 +17,7 @@
 #include "run-command.h"
 #include "parse-options.h"
 #include "string-list.h"
+#include "notes-merge.h"
 
 static const char * const git_notes_usage[] = {
 	"git notes [--ref <notes_ref>] [list [<object>]]",
@@ -25,6 +26,7 @@ static const char * const git_notes_usage[] = {
 	"git notes [--ref <notes_ref>] append [-m <msg> | -F <file> | (-c | -C) <object>] [<object>]",
 	"git notes [--ref <notes_ref>] edit [<object>]",
 	"git notes [--ref <notes_ref>] show [<object>]",
+	"git notes [--ref <notes_ref>] merge [-v | -q] <notes_ref>",
 	"git notes [--ref <notes_ref>] remove [<object>]",
 	"git notes [--ref <notes_ref>] prune [-n | -v]",
 	NULL
@@ -61,6 +63,11 @@ static const char * const git_notes_show_usage[] = {
 	NULL
 };
 
+static const char * const git_notes_merge_usage[] = {
+	"git notes merge [<options>] <notes_ref>",
+	NULL
+};
+
 static const char * const git_notes_remove_usage[] = {
 	"git notes remove [<object>]",
 	NULL
@@ -772,6 +779,50 @@ static int show(int argc, const char **argv, const char *prefix)
 	return retval;
 }
 
+static int merge(int argc, const char **argv, const char *prefix)
+{
+	struct strbuf remote_ref = STRBUF_INIT, msg = STRBUF_INIT;
+	unsigned char result_sha1[20];
+	struct notes_merge_options o;
+	int verbosity = 0, result;
+	struct option options[] = {
+		OPT__VERBOSITY(&verbosity),
+		OPT_END()
+	};
+
+	argc = parse_options(argc, argv, prefix, options,
+			     git_notes_merge_usage, 0);
+
+	if (argc != 1) {
+		error("Must specify a notes ref to merge");
+		usage_with_options(git_notes_merge_usage, options);
+	}
+
+	init_notes_merge_options(&o);
+	o.verbosity = verbosity + 2; // default verbosity level is 2
+	o.local_ref = default_notes_ref();
+	strbuf_addstr(&remote_ref, argv[0]);
+	expand_notes_ref(&remote_ref);
+	o.remote_ref = remote_ref.buf;
+
+	result = notes_merge(&o, result_sha1);
+
+	strbuf_addf(&msg, "notes: Merged notes from %s into %s",
+		    remote_ref.buf, default_notes_ref());
+	if (result == 0) { /* Merge resulted (trivially) in result_sha1 */
+		/* Update default notes ref with new commit */
+		update_ref(msg.buf, default_notes_ref(), result_sha1, NULL,
+			   0, DIE_ON_ERR);
+	} else {
+		/* TODO: */
+		die("'git notes merge' cannot yet handle non-trivial merges!");
+	}
+
+	strbuf_release(&remote_ref);
+	strbuf_release(&msg);
+	return 0;
+}
+
 static int remove_cmd(int argc, const char **argv, const char *prefix)
 {
 	struct option options[] = {
@@ -865,6 +916,8 @@ int cmd_notes(int argc, const char **argv, const char *prefix)
 		result = append_edit(argc, argv, prefix);
 	else if (!strcmp(argv[0], "show"))
 		result = show(argc, argv, prefix);
+	else if (!strcmp(argv[0], "merge"))
+		result = merge(argc, argv, prefix);
 	else if (!strcmp(argv[0], "remove"))
 		result = remove_cmd(argc, argv, prefix);
 	else if (!strcmp(argv[0], "prune"))
diff --git a/notes-merge.c b/notes-merge.c
new file mode 100644
index 0000000..5461827
--- /dev/null
+++ b/notes-merge.c
@@ -0,0 +1,103 @@
+#include "cache.h"
+#include "commit.h"
+#include "notes-merge.h"
+
+void init_notes_merge_options(struct notes_merge_options *o)
+{
+	memset(o, 0, sizeof(struct notes_merge_options));
+	o->verbosity = 2;
+}
+
+static int show(struct notes_merge_options *o, int v)
+{
+	return (o->verbosity >= v) || o->verbosity >= 5;
+}
+
+#define OUTPUT(o, v, ...) \
+	do { if (show((o), (v))) { printf(__VA_ARGS__); puts(""); } } while (0)
+
+int notes_merge(struct notes_merge_options *o,
+		unsigned char *result_sha1)
+{
+	unsigned char local_sha1[20], remote_sha1[20];
+	struct commit *local, *remote;
+	struct commit_list *bases = NULL;
+	const unsigned char *base_sha1;
+	int result = 0;
+
+	hashclr(result_sha1);
+
+	OUTPUT(o, 5, "notes_merge(o->local_ref = %s, o->remote_ref = %s)",
+	       o->local_ref, o->remote_ref);
+
+	if (!o->local_ref || get_sha1(o->local_ref, local_sha1)) {
+		/* empty notes ref => assume empty notes tree */
+		hashclr(local_sha1);
+		local = NULL;
+	} else if (!(local = lookup_commit_reference(local_sha1)))
+		die("Could not parse commit '%s'.", o->local_ref);
+	OUTPUT(o, 5, "\tlocal commit: %.7s", sha1_to_hex(local_sha1));
+
+	if (!o->remote_ref || get_sha1(o->remote_ref, remote_sha1)) {
+		/* empty notes ref => assume empty notes tree */
+		hashclr(remote_sha1);
+		remote = NULL;
+	}
+	if (!(remote = lookup_commit_reference(remote_sha1)))
+		die("Could not parse commit '%s'.", o->remote_ref);
+	OUTPUT(o, 5, "\tremote commit: %.7s", sha1_to_hex(remote_sha1));
+
+	if (!local) {
+		/* result == remote commit */
+		hashcpy(result_sha1, remote_sha1);
+		goto found_result;
+	}
+	if (!remote) {
+		/* result == local commit */
+		hashcpy(result_sha1, local_sha1);
+		goto found_result;
+	}
+	assert(local && remote);
+
+	/* Find merge bases */
+	bases = get_merge_bases(local, remote, 1);
+	if (!bases) {
+		base_sha1 = null_sha1;
+		OUTPUT(o, 4, "No merge base found; doing history-less merge");
+	} else if (!bases->next) {
+		base_sha1 = bases->item->object.sha1;
+		OUTPUT(o, 4, "One merge base found (%.7s)",
+		       sha1_to_hex(base_sha1));
+	} else {
+		/* TODO: How to handle multiple merge-bases? */
+		base_sha1 = bases->item->object.sha1;
+		OUTPUT(o, 3, "Multiple merge bases found. Using the first "
+		       "(%.7s)", sha1_to_hex(base_sha1));
+	}
+
+	OUTPUT(o, 4, "Merging remote commit %.7s into local commit %.7s with "
+	       "merge-base %.7s", sha1_to_hex(remote->object.sha1),
+	       sha1_to_hex(local->object.sha1), sha1_to_hex(base_sha1));
+
+	if (!hashcmp(remote->object.sha1, base_sha1)) {
+		/* Already merged; result == local commit */
+		OUTPUT(o, 2, "Already up-to-date!");
+		hashcpy(result_sha1, local->object.sha1);
+		goto found_result;
+	}
+	if (!hashcmp(local->object.sha1, base_sha1)) {
+		/* Fast-forward; result == remote commit */
+		OUTPUT(o, 2, "Fast-forward");
+		hashcpy(result_sha1, remote->object.sha1);
+		goto found_result;
+	}
+
+	/* TODO: */
+	result = error("notes_merge() cannot yet handle real merges.");
+
+found_result:
+	free_commit_list(bases);
+	OUTPUT(o, 5, "notes_merge(): result = %i, result_sha1 = %.7s",
+	       result, sha1_to_hex(result_sha1));
+	return result;
+}
diff --git a/notes-merge.h b/notes-merge.h
new file mode 100644
index 0000000..c4416e1
--- /dev/null
+++ b/notes-merge.h
@@ -0,0 +1,30 @@
+#ifndef NOTES_MERGE_H
+#define NOTES_MERGE_H
+
+struct notes_merge_options {
+	const char *local_ref;
+	const char *remote_ref;
+	int verbosity;
+};
+
+void init_notes_merge_options(struct notes_merge_options *o);
+
+/*
+ * Merge notes from o->remote_ref into o->local_ref
+ *
+ * The commits given by the two refs are merged, producing one of the following
+ * outcomes:
+ *
+ * 1. The merge trivially results in an existing commit (e.g. fast-forward or
+ *    already-up-to-date). The SHA1 of the result is written into 'result_sha1'
+ *    and 0 is returned.
+ * 2. The merge fails. result_sha1 is set to null_sha1, and non-zero returned.
+ *
+ * Either ref (but not both) may not exist in which case the missing ref is
+ * interpreted as an empty notes tree, and the merge trivially results in
+ * what the other ref points to.
+ */
+int notes_merge(struct notes_merge_options *o,
+		unsigned char *result_sha1);
+
+#endif
diff --git a/t/t3308-notes-merge.sh b/t/t3308-notes-merge.sh
new file mode 100755
index 0000000..0342e37
--- /dev/null
+++ b/t/t3308-notes-merge.sh
@@ -0,0 +1,139 @@
+#!/bin/sh
+#
+# Copyright (c) 2010 Johan Herland
+#
+
+test_description='Test merging of notes trees'
+
+. ./test-lib.sh
+
+test_expect_success setup '
+	test_commit 1st &&
+	test_commit 2nd &&
+	test_commit 3rd &&
+	test_commit 4th &&
+	test_commit 5th &&
+	# Create notes on 4 first commits
+	git config core.notesRef refs/notes/x &&
+	git notes add -m "Notes on 1st commit" 1st &&
+	git notes add -m "Notes on 2nd commit" 2nd &&
+	git notes add -m "Notes on 3rd commit" 3rd &&
+	git notes add -m "Notes on 4th commit" 4th
+'
+
+commit_sha1=$(git rev-parse 1st^{commit})
+commit_sha2=$(git rev-parse 2nd^{commit})
+commit_sha3=$(git rev-parse 3rd^{commit})
+commit_sha4=$(git rev-parse 4th^{commit})
+commit_sha5=$(git rev-parse 5th^{commit})
+
+verify_notes () {
+	notes_ref="$1"
+	git -c core.notesRef="refs/notes/$notes_ref" notes |
+		sort >"output_notes_$notes_ref" &&
+	test_cmp "expect_notes_$notes_ref" "output_notes_$notes_ref" &&
+	git -c core.notesRef="refs/notes/$notes_ref" log --format="%H %s%n%N" \
+		>"output_log_$notes_ref" &&
+	test_cmp "expect_log_$notes_ref" "output_log_$notes_ref"
+}
+
+cat <<EOF | sort >expect_notes_x
+5e93d24084d32e1cb61f7070505b9d2530cca987 $commit_sha4
+8366731eeee53787d2bdf8fc1eff7d94757e8da0 $commit_sha3
+eede89064cd42441590d6afec6c37b321ada3389 $commit_sha2
+daa55ffad6cb99bf64226532147ffcaf5ce8bdd1 $commit_sha1
+EOF
+
+cat >expect_log_x <<EOF
+$commit_sha5 5th
+
+$commit_sha4 4th
+Notes on 4th commit
+
+$commit_sha3 3rd
+Notes on 3rd commit
+
+$commit_sha2 2nd
+Notes on 2nd commit
+
+$commit_sha1 1st
+Notes on 1st commit
+
+EOF
+
+test_expect_success 'verify initial notes (x)' '
+	verify_notes x
+'
+
+cp expect_notes_x expect_notes_y
+cp expect_log_x expect_log_y
+
+test_expect_success 'merge notes into empty notes ref (x => y)' '
+	git config core.notesRef refs/notes/y &&
+	git notes merge x &&
+	verify_notes y &&
+	# x and y should point to the same notes commit
+	test "$(git rev-parse refs/notes/x)" = "$(git rev-parse refs/notes/y)"
+'
+
+test_expect_success 'change notes on other notes ref (y)' '
+	# Not touching notes to 1st commit
+	git notes remove 2nd &&
+	git notes append -m "More notes on 3rd commit" 3rd &&
+	git notes add -f -m "New notes on 4th commit" 4th &&
+	git notes add -m "Notes on 5th commit" 5th
+'
+
+cat <<EOF | sort >expect_notes_y
+0f2efbd00262f2fd41dfae33df8765618eeacd99 $commit_sha5
+dec2502dac3ea161543f71930044deff93fa945c $commit_sha4
+4069cdb399fd45463ec6eef8e051a16a03592d91 $commit_sha3
+daa55ffad6cb99bf64226532147ffcaf5ce8bdd1 $commit_sha1
+EOF
+
+cat >expect_log_y <<EOF
+$commit_sha5 5th
+Notes on 5th commit
+
+$commit_sha4 4th
+New notes on 4th commit
+
+$commit_sha3 3rd
+Notes on 3rd commit
+
+More notes on 3rd commit
+
+$commit_sha2 2nd
+
+$commit_sha1 1st
+Notes on 1st commit
+
+EOF
+
+test_expect_success 'verify changed notes on other notes ref (y)' '
+	verify_notes y
+'
+
+test_expect_success 'verify unchanged notes on original notes ref (x)' '
+	verify_notes x
+'
+
+test_expect_success 'merge original notes (x) into changed notes (y) => No-op' '
+	git notes merge -vvv x &&
+	verify_notes y &&
+	verify_notes x
+'
+
+cp expect_notes_y expect_notes_x
+cp expect_log_y expect_log_x
+
+test_expect_success 'merge changed (y) into original (x) => Fast-forward' '
+	git config core.notesRef refs/notes/x &&
+	git notes merge y &&
+	verify_notes x &&
+	verify_notes y &&
+	# x and y should point to same the notes commit
+	test "$(git rev-parse refs/notes/x)" = "$(git rev-parse refs/notes/y)"
+'
+
+test_done
-- 
1.7.3.98.g5ad7d9

[PATCH 09/18] builtin/notes.c: Refactor creation of notes commits.

[Johan Herland]

Create new function create_notes_commit() which is slightly more general than
commit_notes() (accepts multiple commit parents and does not auto-update the
notes ref). This function will be used by the notes-merge functionality in
future patches.

Also rewrite builtin/notes.c:commit_notes() to reuse this new function.

Signed-off-by: Johan Herland <johan@herland.net>
---
 builtin.h       |    2 +-
 builtin/notes.c |   28 +++++-----------------------
 notes-merge.c   |   27 +++++++++++++++++++++++++++
 notes-merge.h   |   14 ++++++++++++++
 4 files changed, 47 insertions(+), 24 deletions(-)

diff --git a/builtin.h b/builtin.h
index ed6ee26..908d850 100644
--- a/builtin.h
+++ b/builtin.h
@@ -17,7 +17,7 @@ extern void prune_packed_objects(int);
 extern int fmt_merge_msg(int merge_summary, struct strbuf *in,
 	struct strbuf *out);
 extern int fmt_merge_msg_shortlog(struct strbuf *in, struct strbuf *out);
-extern int commit_notes(struct notes_tree *t, const char *msg);
+extern void commit_notes(struct notes_tree *t, const char *msg);
 
 struct notes_rewrite_cfg {
 	struct notes_tree **trees;
diff --git a/builtin/notes.c b/builtin/notes.c
index ec1d042..717548d 100644
--- a/builtin/notes.c
+++ b/builtin/notes.c
@@ -288,18 +288,17 @@ static int parse_reedit_arg(const struct option *opt, const char *arg, int unset
 	return parse_reuse_arg(opt, arg, unset);
 }
 
-int commit_notes(struct notes_tree *t, const char *msg)
+void commit_notes(struct notes_tree *t, const char *msg)
 {
-	struct commit_list *parent;
-	unsigned char tree_sha1[20], prev_commit[20], new_commit[20];
 	struct strbuf buf = STRBUF_INIT;
+	unsigned char commit_sha1[20];
 
 	if (!t)
 		t = &default_notes_tree;
 	if (!t->initialized || !t->ref || !*t->ref)
 		die("Cannot commit uninitialized/unreferenced notes tree");
 	if (!t->dirty)
-		return 0; /* don't have to commit an unchanged tree */
+		return; /* don't have to commit an unchanged tree */
 
 	/* Prepare commit message and reflog message */
 	strbuf_addstr(&buf, "notes: "); /* commit message starts at index 7 */
@@ -307,27 +306,10 @@ int commit_notes(struct notes_tree *t, const char *msg)
 	if (buf.buf[buf.len - 1] != '\n')
 		strbuf_addch(&buf, '\n'); /* Make sure msg ends with newline */
 
-	/* Convert notes tree to tree object */
-	if (write_notes_tree(t, tree_sha1))
-		die("Failed to write current notes tree to database");
-
-	/* Create new commit for the tree object */
-	if (!read_ref(t->ref, prev_commit)) { /* retrieve parent commit */
-		parent = xmalloc(sizeof(*parent));
-		parent->item = lookup_commit(prev_commit);
-		parent->next = NULL;
-	} else {
-		hashclr(prev_commit);
-		parent = NULL;
-	}
-	if (commit_tree(buf.buf + 7, tree_sha1, parent, new_commit, NULL))
-		die("Failed to commit notes tree to database");
-
-	/* Update notes ref with new commit */
-	update_ref(buf.buf, t->ref, new_commit, prev_commit, 0, DIE_ON_ERR);
+	create_notes_commit(t, NULL, buf.buf + 7, commit_sha1);
+	update_ref(buf.buf, t->ref, commit_sha1, NULL, 0, DIE_ON_ERR);
 
 	strbuf_release(&buf);
-	return 0;
 }
 
 combine_notes_fn parse_combine_notes_fn(const char *v)
diff --git a/notes-merge.c b/notes-merge.c
index 5461827..9a4dc6d 100644
--- a/notes-merge.c
+++ b/notes-merge.c
@@ -1,5 +1,6 @@
 #include "cache.h"
 #include "commit.h"
+#include "notes.h"
 #include "notes-merge.h"
 
 void init_notes_merge_options(struct notes_merge_options *o)
@@ -16,6 +17,32 @@ static int show(struct notes_merge_options *o, int v)
 #define OUTPUT(o, v, ...) \
 	do { if (show((o), (v))) { printf(__VA_ARGS__); puts(""); } } while (0)
 
+void create_notes_commit(struct notes_tree *t, struct commit_list *parents,
+			 const char *msg, unsigned char *result_sha1)
+{
+	unsigned char tree_sha1[20];
+
+	assert(t->initialized);
+
+	if (write_notes_tree(t, tree_sha1))
+		die("Failed to write notes tree to database");
+
+	if (!parents) {
+		/* Deduce parent commit from t->ref */
+		unsigned char parent_sha1[20];
+		if (!read_ref(t->ref, parent_sha1)) {
+			struct commit *parent = lookup_commit(parent_sha1);
+			if (!parent || parse_commit(parent))
+				die("Failed to find/parse commit %s", t->ref);
+			commit_list_insert(parent, &parents);
+		}
+		/* else: t->ref points to nothing, assume root/orphan commit */
+	}
+
+	if (commit_tree(msg, tree_sha1, parents, result_sha1, NULL))
+		die("Failed to commit notes tree to database");
+}
+
 int notes_merge(struct notes_merge_options *o,
 		unsigned char *result_sha1)
 {
diff --git a/notes-merge.h b/notes-merge.h
index c4416e1..b570123 100644
--- a/notes-merge.h
+++ b/notes-merge.h
@@ -10,6 +10,20 @@ struct notes_merge_options {
 void init_notes_merge_options(struct notes_merge_options *o);
 
 /*
+ * Create new notes commit from the given notes tree
+ *
+ * Properties of the created commit:
+ * - tree: the result of converting t to a tree object with write_notes_tree().
+ * - parents: the given parents OR (if NULL) the commit referenced by t->ref.
+ * - author/committer: the default determined by commmit_tree().
+ * - commit message: msg
+ *
+ * The resulting commit SHA1 is stored in result_sha1.
+ */
+void create_notes_commit(struct notes_tree *t, struct commit_list *parents,
+			 const char *msg, unsigned char *result_sha1);
+
+/*
  * Merge notes from o->remote_ref into o->local_ref
  *
  * The commits given by the two refs are merged, producing one of the following
-- 
1.7.3.98.g5ad7d9

[PATCH 10/18] git notes merge: Handle real, non-conflicting notes merges

[Johan Herland]

This continuation of the 'git notes merge' implementation teaches notes-merge
to properly do real merges between notes trees: Two diffs are performed, one
from $base to $remote, and another from $base to $local. The paths in each
diff are normalized to SHA1 object names. The two diffs are then consolidated
into a single list of change pairs to be evaluated. Each change pair consist
of:

  - The annotated object's SHA1
  - The $base SHA1 (i.e. the common ancestor notes for this object)
  - The $local SHA1 (i.e. the current notes for this object)
  - The $remote SHA1 (i.e. the to-be-merged notes for this object)

>From the pair ($base -> $local, $base -> $remote), we can determine the merge
result using regular 3-way rules. If conflicts are encountered in this
process, we fail loudly and exit (conflict handling to be added in a future
patch), If we can complete the merge without conflicts, the resulting
notes tree is committed, and the current notes ref updated.

The patch includes added testcases verifying that we can successfully do real
conflict-less merges.

This patch has been improved by the following contributions:
- Jonathan Nieder: Future-proof by always checking add_note() return value
- Stephen Boyd: Use test_commit

Cc: Jonathan Nieder <jrnieder@gmail.com>
Cc: Stephen Boyd <bebarino@gmail.com>
Signed-off-by: Johan Herland <johan@herland.net>
---
 builtin/notes.c        |   15 ++-
 notes-merge.c          |  325 +++++++++++++++++++++++++++++++++++++++++++++++-
 notes-merge.h          |   15 ++-
 t/t3308-notes-merge.sh |  188 ++++++++++++++++++++++++++++
 4 files changed, 532 insertions(+), 11 deletions(-)

diff --git a/builtin/notes.c b/builtin/notes.c
index 717548d..82d2ffe 100644
--- a/builtin/notes.c
+++ b/builtin/notes.c
@@ -765,6 +765,7 @@ static int merge(int argc, const char **argv, const char *prefix)
 {
 	struct strbuf remote_ref = STRBUF_INIT, msg = STRBUF_INIT;
 	unsigned char result_sha1[20];
+	struct notes_tree *t;
 	struct notes_merge_options o;
 	int verbosity = 0, result;
 	struct option options[] = {
@@ -787,19 +788,23 @@ static int merge(int argc, const char **argv, const char *prefix)
 	expand_notes_ref(&remote_ref);
 	o.remote_ref = remote_ref.buf;
 
-	result = notes_merge(&o, result_sha1);
+	t = init_notes_check("merge");
 
 	strbuf_addf(&msg, "notes: Merged notes from %s into %s",
 		    remote_ref.buf, default_notes_ref());
-	if (result == 0) { /* Merge resulted (trivially) in result_sha1 */
+	o.commit_msg = msg.buf + 7; // skip "notes: " prefix
+
+	result = notes_merge(&o, t, result_sha1);
+
+	if (result >= 0) /* Merge resulted (trivially) in result_sha1 */
 		/* Update default notes ref with new commit */
 		update_ref(msg.buf, default_notes_ref(), result_sha1, NULL,
 			   0, DIE_ON_ERR);
-	} else {
+	else
 		/* TODO: */
-		die("'git notes merge' cannot yet handle non-trivial merges!");
-	}
+		die("'git notes merge' cannot yet handle conflicts!");
 
+	free_notes(t);
 	strbuf_release(&remote_ref);
 	strbuf_release(&msg);
 	return 0;
diff --git a/notes-merge.c b/notes-merge.c
index 9a4dc6d..f625ebd 100644
--- a/notes-merge.c
+++ b/notes-merge.c
@@ -1,8 +1,14 @@
 #include "cache.h"
 #include "commit.h"
+#include "diff.h"
+#include "diffcore.h"
 #include "notes.h"
 #include "notes-merge.h"
 
+struct notes_merge_pair {
+	unsigned char obj[20], base[20], local[20], remote[20];
+};
+
 void init_notes_merge_options(struct notes_merge_options *o)
 {
 	memset(o, 0, sizeof(struct notes_merge_options));
@@ -17,6 +23,305 @@ static int show(struct notes_merge_options *o, int v)
 #define OUTPUT(o, v, ...) \
 	do { if (show((o), (v))) { printf(__VA_ARGS__); puts(""); } } while (0)
 
+static int path_to_sha1(const char *path, unsigned char *sha1)
+{
+	char hex_sha1[40];
+	int i = 0;
+	while (*path && i < 40) {
+		if (*path != '/')
+			hex_sha1[i++] = *path;
+		path++;
+	}
+	if (*path || i != 40)
+		return -1;
+	return get_sha1_hex(hex_sha1, sha1);
+}
+
+static int verify_notes_filepair(struct diff_filepair *p, unsigned char *sha1)
+{
+	switch (p->status) {
+	case DIFF_STATUS_MODIFIED:
+		assert(p->one->mode == p->two->mode);
+		assert(!is_null_sha1(p->one->sha1));
+		assert(!is_null_sha1(p->two->sha1));
+		break;
+	case DIFF_STATUS_ADDED:
+		assert(is_null_sha1(p->one->sha1));
+		break;
+	case DIFF_STATUS_DELETED:
+		assert(is_null_sha1(p->two->sha1));
+		break;
+	default:
+		return -1;
+	}
+	assert(!strcmp(p->one->path, p->two->path));
+	return path_to_sha1(p->one->path, sha1);
+}
+
+static struct notes_merge_pair *find_notes_merge_pair_pos(
+		struct notes_merge_pair *list, int len, unsigned char *obj,
+		int insert_new, int *occupied)
+{
+	/*
+	 * Both diff_tree_remote() and diff_tree_local() tend to process
+	 * merge_pairs in ascending order. Therefore, cache last returned
+	 * index, and search sequentially from there until the appropriate
+	 * position is found.
+	 *
+	 * Since inserts only happen from diff_tree_remote() (which mainly
+	 * _appends_), we don't care that inserting into the middle of the
+	 * list is expensive (using memmove()).
+	 */
+	static int last_index = 0;
+	int i = last_index < len ? last_index : len - 1;
+	int prev_cmp = 0, cmp = -1;
+	while (i >= 0 && i < len) {
+		cmp = hashcmp(obj, list[i].obj);
+		if (!cmp) /* obj belongs @ i */
+			break;
+		else if (cmp < 0 && prev_cmp <= 0) /* obj belongs < i */
+			i--;
+		else if (cmp < 0) /* obj belongs between i-1 and i */
+			break;
+		else if (cmp > 0 && prev_cmp >= 0) /* obj belongs > i */
+			i++;
+		else /* if (cmp > 0) */ { /* obj belongs between i and i+1 */
+			i++;
+			break;
+		}
+		prev_cmp = cmp;
+	}
+	if (i < 0)
+		i = 0;
+	/* obj belongs at, or immediately preceding, index i (0 <= i <= len) */
+
+	if (!cmp)
+		*occupied = 1;
+	else {
+		*occupied = 0;
+		if (insert_new && i < len) {
+			memmove(list + i + 1, list + i,
+				(len - i) * sizeof(struct notes_merge_pair));
+			memset(list + i, 0, sizeof(struct notes_merge_pair));
+		}
+	}
+	last_index = i;
+	return list + i;
+}
+
+static unsigned char uninitialized[20] =
+	"\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff" \
+	"\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff";
+
+static struct notes_merge_pair *diff_tree_remote(struct notes_merge_options *o,
+						 const unsigned char *base,
+						 const unsigned char *remote,
+						 int *num_changes)
+{
+	struct diff_options opt;
+	struct notes_merge_pair *changes;
+	int i, len = 0;
+
+	OUTPUT(o, 5, "\tdiff_tree_remote(base = %.7s, remote = %.7s)",
+	       sha1_to_hex(base), sha1_to_hex(remote));
+
+	diff_setup(&opt);
+	DIFF_OPT_SET(&opt, RECURSIVE);
+	opt.output_format = DIFF_FORMAT_NO_OUTPUT;
+	if (diff_setup_done(&opt) < 0)
+		die("diff_setup_done failed");
+	diff_tree_sha1(base, remote, "", &opt);
+	diffcore_std(&opt);
+
+	changes = xcalloc(diff_queued_diff.nr, sizeof(struct notes_merge_pair));
+
+	for (i = 0; i < diff_queued_diff.nr; i++) {
+		struct diff_filepair *p = diff_queued_diff.queue[i];
+		struct notes_merge_pair *mp;
+		int occupied;
+		unsigned char obj[20];
+
+		if (verify_notes_filepair(p, obj)) {
+			OUTPUT(o, 5, "\t\tCannot merge entry '%s' (%c): "
+			       "%.7s -> %.7s. Skipping!", p->one->path,
+			       p->status, sha1_to_hex(p->one->sha1),
+			       sha1_to_hex(p->two->sha1));
+			continue;
+		}
+		mp = find_notes_merge_pair_pos(changes, len, obj, 1, &occupied);
+		if (occupied) {
+			/* We've found an addition/deletion pair */
+			assert(!hashcmp(mp->obj, obj));
+			if (is_null_sha1(p->one->sha1)) { /* addition */
+				assert(is_null_sha1(mp->remote));
+				hashcpy(mp->remote, p->two->sha1);
+			} else if (is_null_sha1(p->two->sha1)) { /* deletion */
+				assert(is_null_sha1(mp->base));
+				hashcpy(mp->base, p->one->sha1);
+			} else
+				assert(!"Invalid existing change recorded");
+		} else {
+			hashcpy(mp->obj, obj);
+			hashcpy(mp->base, p->one->sha1);
+			hashcpy(mp->local, uninitialized);
+			hashcpy(mp->remote, p->two->sha1);
+			len++;
+		}
+		OUTPUT(o, 5, "\t\tRecorded remote change for %s: %.7s -> %.7s",
+		       sha1_to_hex(mp->obj), sha1_to_hex(mp->base),
+		       sha1_to_hex(mp->remote));
+	}
+	diff_flush(&opt);
+	diff_tree_release_paths(&opt);
+
+	*num_changes = len;
+	return changes;
+}
+
+static void diff_tree_local(struct notes_merge_options *o,
+			    struct notes_merge_pair *changes, int len,
+			    const unsigned char *base,
+			    const unsigned char *local)
+{
+	struct diff_options opt;
+	int i;
+
+	OUTPUT(o, 5, "\tdiff_tree_local(len = %i, base = %.7s, local = %.7s)",
+	       len, sha1_to_hex(base), sha1_to_hex(local));
+
+	diff_setup(&opt);
+	DIFF_OPT_SET(&opt, RECURSIVE);
+	opt.output_format = DIFF_FORMAT_NO_OUTPUT;
+	if (diff_setup_done(&opt) < 0)
+		die("diff_setup_done failed");
+	diff_tree_sha1(base, local, "", &opt);
+	diffcore_std(&opt);
+
+	for (i = 0; i < diff_queued_diff.nr; i++) {
+		struct diff_filepair *p = diff_queued_diff.queue[i];
+		struct notes_merge_pair *mp;
+		int match;
+		unsigned char obj[20];
+
+		if (verify_notes_filepair(p, obj)) {
+			OUTPUT(o, 5, "\t\tCannot merge entry '%s' (%c): "
+			       "%.7s -> %.7s. Skipping!", p->one->path,
+			       p->status, sha1_to_hex(p->one->sha1),
+			       sha1_to_hex(p->two->sha1));
+			continue;
+		}
+		mp = find_notes_merge_pair_pos(changes, len, obj, 0, &match);
+		if (!match) {
+			OUTPUT(o, 5, "\t\tIgnoring local-only change for %s: "
+			       "%.7s -> %.7s", sha1_to_hex(obj),
+			       sha1_to_hex(p->one->sha1),
+			       sha1_to_hex(p->two->sha1));
+			continue;
+		}
+
+		assert(!hashcmp(mp->obj, obj));
+		if (is_null_sha1(p->two->sha1)) { /* deletion */
+			/*
+			 * Either this is a true deletion (1), or it is part
+			 * of an A/D pair (2), or D/A pair (3):
+			 *
+			 * (1) mp->local is uninitialized; set it to null_sha1
+			 * (2) mp->local is not uninitialized; don't touch it
+			 * (3) mp->local is uninitialized; set it to null_sha1
+			 *     (will be overwritten by following addition)
+			 */
+			if (!hashcmp(mp->local, uninitialized))
+				hashclr(mp->local);
+		} else if (is_null_sha1(p->one->sha1)) { /* addition */
+			/*
+			 * Either this is a true addition (1), or it is part
+			 * of an A/D pair (2), or D/A pair (3):
+			 *
+			 * (1) mp->local is uninitialized; set to p->two->sha1
+			 * (2) mp->local is uninitialized; set to p->two->sha1
+			 * (3) mp->local is null_sha1;     set to p->two->sha1
+			 */
+			assert(is_null_sha1(mp->local) ||
+			       !hashcmp(mp->local, uninitialized));
+			hashcpy(mp->local, p->two->sha1);
+		} else { /* modification */
+			/*
+			 * This is a true modification. p->one->sha1 shall
+			 * match mp->base, and mp->local shall be uninitialized.
+			 * Set mp->local to p->two->sha1.
+			 */
+			assert(!hashcmp(p->one->sha1, mp->base));
+			assert(!hashcmp(mp->local, uninitialized));
+			hashcpy(mp->local, p->two->sha1);
+		}
+		OUTPUT(o, 5, "\t\tRecorded local change for %s: %.7s -> %.7s",
+		       sha1_to_hex(mp->obj), sha1_to_hex(mp->base),
+		       sha1_to_hex(mp->local));
+	}
+	diff_flush(&opt);
+	diff_tree_release_paths(&opt);
+}
+
+static int merge_changes(struct notes_merge_options *o,
+			 struct notes_merge_pair *changes, int *num_changes,
+			 struct notes_tree *t)
+{
+	int i, conflicts = 0;
+
+	OUTPUT(o, 5, "\tmerge_changes(num_changes = %i)", *num_changes);
+	for (i = 0; i < *num_changes; i++) {
+		struct notes_merge_pair *p = changes + i;
+		OUTPUT(o, 5, "\t\t%.7s: %.7s -> %.7s/%.7s",
+		       sha1_to_hex(p->obj), sha1_to_hex(p->base),
+		       sha1_to_hex(p->local), sha1_to_hex(p->remote));
+
+		if (!hashcmp(p->base, p->remote)) {
+			/* no remote change; nothing to do */
+			OUTPUT(o, 5, "\t\t\tskipping (no remote change)");
+		} else if (!hashcmp(p->local, p->remote)) {
+			/* same change in local and remote; nothing to do */
+			OUTPUT(o, 5, "\t\t\tskipping (local == remote)");
+		} else if (!hashcmp(p->local, uninitialized) ||
+			   !hashcmp(p->local, p->base)) {
+			/* no local change; adopt remote change */
+			OUTPUT(o, 5, "\t\t\tno local change, adopting remote");
+			if (add_note(t, p->obj, p->remote,
+				     combine_notes_overwrite))
+				die("confused: combine_notes_overwrite failed");
+		} else {
+			/* need file-level merge between local and remote */
+			OUTPUT(o, 5, "\t\t\tneed content-level merge");
+			conflicts += 1; /* TODO */
+		}
+	}
+
+	return conflicts;
+}
+
+static int merge_from_diffs(struct notes_merge_options *o,
+			    const unsigned char *base,
+			    const unsigned char *local,
+			    const unsigned char *remote, struct notes_tree *t)
+{
+	struct notes_merge_pair *changes;
+	int num_changes, conflicts;
+
+	OUTPUT(o, 5, "\tmerge_from_diffs(base = %.7s, local = %.7s, "
+	       "remote = %.7s)", sha1_to_hex(base), sha1_to_hex(local),
+	       sha1_to_hex(remote));
+
+	changes = diff_tree_remote(o, base, remote, &num_changes);
+	diff_tree_local(o, changes, num_changes, base, local);
+
+	conflicts = merge_changes(o, changes, &num_changes, t);
+	free(changes);
+
+	OUTPUT(o, 4, "Merge result: %i unmerged notes and a %s notes tree",
+	       conflicts, t->dirty ? "dirty" : "clean");
+
+	return conflicts ? -1 : 1;
+}
+
 void create_notes_commit(struct notes_tree *t, struct commit_list *parents,
 			 const char *msg, unsigned char *result_sha1)
 {
@@ -44,14 +349,16 @@ void create_notes_commit(struct notes_tree *t, struct commit_list *parents,
 }
 
 int notes_merge(struct notes_merge_options *o,
+		struct notes_tree *local_tree,
 		unsigned char *result_sha1)
 {
 	unsigned char local_sha1[20], remote_sha1[20];
 	struct commit *local, *remote;
 	struct commit_list *bases = NULL;
-	const unsigned char *base_sha1;
+	const unsigned char *base_sha1, *base_tree_sha1;
 	int result = 0;
 
+	assert(!strcmp(o->local_ref, local_tree->ref));
 	hashclr(result_sha1);
 
 	OUTPUT(o, 5, "notes_merge(o->local_ref = %s, o->remote_ref = %s)",
@@ -90,14 +397,17 @@ int notes_merge(struct notes_merge_options *o,
 	bases = get_merge_bases(local, remote, 1);
 	if (!bases) {
 		base_sha1 = null_sha1;
+		base_tree_sha1 = (unsigned char *)EMPTY_TREE_SHA1_BIN;
 		OUTPUT(o, 4, "No merge base found; doing history-less merge");
 	} else if (!bases->next) {
 		base_sha1 = bases->item->object.sha1;
+		base_tree_sha1 = bases->item->tree->object.sha1;
 		OUTPUT(o, 4, "One merge base found (%.7s)",
 		       sha1_to_hex(base_sha1));
 	} else {
 		/* TODO: How to handle multiple merge-bases? */
 		base_sha1 = bases->item->object.sha1;
+		base_tree_sha1 = bases->item->tree->object.sha1;
 		OUTPUT(o, 3, "Multiple merge bases found. Using the first "
 		       "(%.7s)", sha1_to_hex(base_sha1));
 	}
@@ -119,8 +429,17 @@ int notes_merge(struct notes_merge_options *o,
 		goto found_result;
 	}
 
-	/* TODO: */
-	result = error("notes_merge() cannot yet handle real merges.");
+	result = merge_from_diffs(o, base_tree_sha1, local->tree->object.sha1,
+				  remote->tree->object.sha1, local_tree);
+
+	if (result > 0) { /* successful non-trivial merge */
+		/* Commit result */
+		struct commit_list *parents = NULL;
+		commit_list_insert(remote, &parents); /* LIFO order */
+		commit_list_insert(local, &parents);
+		create_notes_commit(local_tree, parents, o->commit_msg,
+				    result_sha1);
+	}
 
 found_result:
 	free_commit_list(bases);
diff --git a/notes-merge.h b/notes-merge.h
index b570123..e42ce4b 100644
--- a/notes-merge.h
+++ b/notes-merge.h
@@ -4,6 +4,7 @@
 struct notes_merge_options {
 	const char *local_ref;
 	const char *remote_ref;
+	const char *commit_msg;
 	int verbosity;
 };
 
@@ -26,19 +27,27 @@ void create_notes_commit(struct notes_tree *t, struct commit_list *parents,
 /*
  * Merge notes from o->remote_ref into o->local_ref
  *
+ * The given notes_tree 'local_tree' must be the notes_tree referenced by the
+ * o->local_ref. This is the notes_tree in which the object-level merge is
+ * performed.
+ *
  * The commits given by the two refs are merged, producing one of the following
  * outcomes:
  *
  * 1. The merge trivially results in an existing commit (e.g. fast-forward or
- *    already-up-to-date). The SHA1 of the result is written into 'result_sha1'
- *    and 0 is returned.
- * 2. The merge fails. result_sha1 is set to null_sha1, and non-zero returned.
+ *    already-up-to-date). 'local_tree' is untouched, the SHA1 of the result
+ *    is written into 'result_sha1' and 0 is returned.
+ * 2. The merge successfully completes, producing a merge commit. local_tree
+ *    contains the updated notes tree, the SHA1 of the resulting commit is
+ *    written into 'result_sha1', and 1 is returned.
+ * 3. The merge fails. result_sha1 is set to null_sha1, and -1 is returned.
  *
  * Either ref (but not both) may not exist in which case the missing ref is
  * interpreted as an empty notes tree, and the merge trivially results in
  * what the other ref points to.
  */
 int notes_merge(struct notes_merge_options *o,
+		struct notes_tree *local_tree,
 		unsigned char *result_sha1);
 
 #endif
diff --git a/t/t3308-notes-merge.sh b/t/t3308-notes-merge.sh
index 0342e37..b211e82 100755
--- a/t/t3308-notes-merge.sh
+++ b/t/t3308-notes-merge.sh
@@ -136,4 +136,192 @@ test_expect_success 'merge changed (y) into original (x) => Fast-forward' '
 	test "$(git rev-parse refs/notes/x)" = "$(git rev-parse refs/notes/y)"
 '
 
+test_expect_success 'merge empty notes ref (z => y)' '
+	# Prepare empty (but valid) notes ref (z)
+	git config core.notesRef refs/notes/z &&
+	git notes add -m "foo" &&
+	git notes remove &&
+	git notes >output_notes_z &&
+	test_cmp /dev/null output_notes_z &&
+	# Do the merge (z => y)
+	git config core.notesRef refs/notes/y &&
+	git notes merge z &&
+	verify_notes y &&
+	# y should no longer point to the same notes commit as x
+	test "$(git rev-parse refs/notes/x)" != "$(git rev-parse refs/notes/y)"
+'
+
+cat <<EOF | sort >expect_notes_y
+0f2efbd00262f2fd41dfae33df8765618eeacd99 $commit_sha5
+dec2502dac3ea161543f71930044deff93fa945c $commit_sha4
+4069cdb399fd45463ec6eef8e051a16a03592d91 $commit_sha3
+d000d30e6ddcfce3a8122c403226a2ce2fd04d9d $commit_sha2
+43add6bd0c8c0bc871ac7991e0f5573cfba27804 $commit_sha1
+EOF
+
+cat >expect_log_y <<EOF
+$commit_sha5 5th
+Notes on 5th commit
+
+$commit_sha4 4th
+New notes on 4th commit
+
+$commit_sha3 3rd
+Notes on 3rd commit
+
+More notes on 3rd commit
+
+$commit_sha2 2nd
+New notes on 2nd commit
+
+$commit_sha1 1st
+Notes on 1st commit
+
+More notes on 1st commit
+
+EOF
+
+test_expect_success 'change notes on other notes ref (y)' '
+	# Append to 1st commit notes
+	git notes append -m "More notes on 1st commit" 1st &&
+	# Add new notes to 2nd commit
+	git notes add -m "New notes on 2nd commit" 2nd &&
+	verify_notes y
+'
+
+cat <<EOF | sort >expect_notes_x
+0f2efbd00262f2fd41dfae33df8765618eeacd99 $commit_sha5
+1f257a3a90328557c452f0817d6cc50c89d315d4 $commit_sha4
+daa55ffad6cb99bf64226532147ffcaf5ce8bdd1 $commit_sha1
+EOF
+
+cat >expect_log_x <<EOF
+$commit_sha5 5th
+Notes on 5th commit
+
+$commit_sha4 4th
+New notes on 4th commit
+
+More notes on 4th commit
+
+$commit_sha3 3rd
+
+$commit_sha2 2nd
+
+$commit_sha1 1st
+Notes on 1st commit
+
+EOF
+
+test_expect_success 'change notes on notes ref (x)' '
+	git config core.notesRef refs/notes/x &&
+	git notes remove 3rd &&
+	git notes append -m "More notes on 4th commit" 4th &&
+	verify_notes x
+'
+
+cat <<EOF | sort >expect_notes_x
+0f2efbd00262f2fd41dfae33df8765618eeacd99 $commit_sha5
+1f257a3a90328557c452f0817d6cc50c89d315d4 $commit_sha4
+d000d30e6ddcfce3a8122c403226a2ce2fd04d9d $commit_sha2
+43add6bd0c8c0bc871ac7991e0f5573cfba27804 $commit_sha1
+EOF
+
+cat >expect_log_x <<EOF
+$commit_sha5 5th
+Notes on 5th commit
+
+$commit_sha4 4th
+New notes on 4th commit
+
+More notes on 4th commit
+
+$commit_sha3 3rd
+
+$commit_sha2 2nd
+New notes on 2nd commit
+
+$commit_sha1 1st
+Notes on 1st commit
+
+More notes on 1st commit
+
+EOF
+
+test_expect_success 'merge y into x => Non-conflicting 3-way merge' '
+	git notes merge y &&
+	verify_notes x &&
+	verify_notes y
+'
+
+cat <<EOF | sort >expect_notes_w
+05a4927951bcef347f51486575b878b2b60137f2 $commit_sha3
+d000d30e6ddcfce3a8122c403226a2ce2fd04d9d $commit_sha2
+EOF
+
+cat >expect_log_w <<EOF
+$commit_sha5 5th
+
+$commit_sha4 4th
+
+$commit_sha3 3rd
+New notes on 3rd commit
+
+$commit_sha2 2nd
+New notes on 2nd commit
+
+$commit_sha1 1st
+
+EOF
+
+test_expect_success 'create notes on new, separate notes ref (w)' '
+	git config core.notesRef refs/notes/w &&
+	# Add same note as refs/notes/y on 2nd commit
+	git notes add -m "New notes on 2nd commit" 2nd &&
+	# Add new note on 3rd commit (non-conflicting)
+	git notes add -m "New notes on 3rd commit" 3rd &&
+	# Verify state of notes on new, separate notes ref (w)
+	verify_notes w
+'
+
+cat <<EOF | sort >expect_notes_x
+0f2efbd00262f2fd41dfae33df8765618eeacd99 $commit_sha5
+1f257a3a90328557c452f0817d6cc50c89d315d4 $commit_sha4
+05a4927951bcef347f51486575b878b2b60137f2 $commit_sha3
+d000d30e6ddcfce3a8122c403226a2ce2fd04d9d $commit_sha2
+43add6bd0c8c0bc871ac7991e0f5573cfba27804 $commit_sha1
+EOF
+
+cat >expect_log_x <<EOF
+$commit_sha5 5th
+Notes on 5th commit
+
+$commit_sha4 4th
+New notes on 4th commit
+
+More notes on 4th commit
+
+$commit_sha3 3rd
+New notes on 3rd commit
+
+$commit_sha2 2nd
+New notes on 2nd commit
+
+$commit_sha1 1st
+Notes on 1st commit
+
+More notes on 1st commit
+
+EOF
+
+test_expect_success 'merge w into x => Non-conflicting history-less merge' '
+	git config core.notesRef refs/notes/x &&
+	git notes merge w &&
+	# Verify new state of notes on other notes ref (x)
+	verify_notes x &&
+	# Also verify that nothing changed on other notes refs (y and w)
+	verify_notes y &&
+	verify_notes w
+'
+
 test_done
-- 
1.7.3.98.g5ad7d9

[PATCH 11/18] git notes merge: Add automatic conflict resolvers (ours, theirs, union)

[Johan Herland]

The new -s/--strategy command-line option to 'git notes merge' allow the user
to choose how notes merge conflicts should be resolved. There are four valid
strategies to choose from:

1. "manual" (the default): This will let the user manually resolve conflicts.
   This option currently fails with an error message. It will be implemented
   properly in future patches.

2. "ours": This automatically chooses the local version of a conflict, and
   discards the remote version.

3. "theirs": This automatically chooses the remote version of a conflict, and
   discards the local version.

4. "union": This automatically resolves the conflict by appending the remote
   version to the local version.

The strategies are implemented using the combine_notes_* functions from the
notes.h API.

The patch also includes testcases verifying the correct implementation of
these strategies.

This patch has been improved by the following contributions:
- Jonathan Nieder: Future-proof by always checking add_note() return value
- Stephen Boyd: Use test_commit

Cc: Jonathan Nieder <jrnieder@gmail.com>
Cc: Stephen Boyd <bebarino@gmail.com>
Signed-off-by: Johan Herland <johan@herland.net>
---
 builtin/notes.c                     |   21 ++-
 notes-merge.c                       |   31 ++-
 notes-merge.h                       |    6 +
 t/t3309-notes-merge-auto-resolve.sh |  502 +++++++++++++++++++++++++++++++++++
 4 files changed, 558 insertions(+), 2 deletions(-)
 create mode 100755 t/t3309-notes-merge-auto-resolve.sh

diff --git a/builtin/notes.c b/builtin/notes.c
index 82d2ffe..79290db 100644
--- a/builtin/notes.c
+++ b/builtin/notes.c
@@ -26,7 +26,7 @@ static const char * const git_notes_usage[] = {
 	"git notes [--ref <notes_ref>] append [-m <msg> | -F <file> | (-c | -C) <object>] [<object>]",
 	"git notes [--ref <notes_ref>] edit [<object>]",
 	"git notes [--ref <notes_ref>] show [<object>]",
-	"git notes [--ref <notes_ref>] merge [-v | -q] <notes_ref>",
+	"git notes [--ref <notes_ref>] merge [-v | -q] [-s <strategy> ] <notes_ref>",
 	"git notes [--ref <notes_ref>] remove [<object>]",
 	"git notes [--ref <notes_ref>] prune [-n | -v]",
 	NULL
@@ -768,8 +768,12 @@ static int merge(int argc, const char **argv, const char *prefix)
 	struct notes_tree *t;
 	struct notes_merge_options o;
 	int verbosity = 0, result;
+	const char *strategy = NULL;
 	struct option options[] = {
 		OPT__VERBOSITY(&verbosity),
+		OPT_STRING('s', "strategy", &strategy, "strategy",
+			   "resolve notes conflicts using the given "
+			   "strategy (manual/ours/theirs/union)"),
 		OPT_END()
 	};
 
@@ -788,6 +792,21 @@ static int merge(int argc, const char **argv, const char *prefix)
 	expand_notes_ref(&remote_ref);
 	o.remote_ref = remote_ref.buf;
 
+	if (strategy) {
+		if (!strcmp(strategy, "manual"))
+			o.strategy = NOTES_MERGE_RESOLVE_MANUAL;
+		else if (!strcmp(strategy, "ours"))
+			o.strategy = NOTES_MERGE_RESOLVE_OURS;
+		else if (!strcmp(strategy, "theirs"))
+			o.strategy = NOTES_MERGE_RESOLVE_THEIRS;
+		else if (!strcmp(strategy, "union"))
+			o.strategy = NOTES_MERGE_RESOLVE_UNION;
+		else {
+			error("Unknown -X/--resolve strategy: %s", strategy);
+			usage_with_options(git_notes_merge_usage, options);
+		}
+	}
+
 	t = init_notes_check("merge");
 
 	strbuf_addf(&msg, "notes: Merged notes from %s into %s",
diff --git a/notes-merge.c b/notes-merge.c
index f625ebd..6fa59d8 100644
--- a/notes-merge.c
+++ b/notes-merge.c
@@ -262,6 +262,35 @@ static void diff_tree_local(struct notes_merge_options *o,
 	diff_tree_release_paths(&opt);
 }
 
+static int merge_one_change(struct notes_merge_options *o,
+			    struct notes_merge_pair *p, struct notes_tree *t)
+{
+	/*
+	 * Return 0 if change was resolved (and added to notes_tree),
+	 * 1 if conflict
+	 */
+	switch (o->strategy) {
+	case NOTES_MERGE_RESOLVE_MANUAL:
+		return 1;
+	case NOTES_MERGE_RESOLVE_OURS:
+		OUTPUT(o, 2, "Using local notes for %s", sha1_to_hex(p->obj));
+		/* nothing to do */
+		return 0;
+	case NOTES_MERGE_RESOLVE_THEIRS:
+		OUTPUT(o, 2, "Using remote notes for %s", sha1_to_hex(p->obj));
+		if (add_note(t, p->obj, p->remote, combine_notes_overwrite))
+			die("confused: combine_notes_overwrite failed");
+		return 0;
+	case NOTES_MERGE_RESOLVE_UNION:
+		OUTPUT(o, 2, "Concatenating local and remote notes for %s",
+		       sha1_to_hex(p->obj));
+		if (add_note(t, p->obj, p->remote, combine_notes_concatenate))
+			die("confused: combine_notes_concatenate failed");
+		return 0;
+	}
+	die("Unknown strategy (%i).", o->strategy);
+}
+
 static int merge_changes(struct notes_merge_options *o,
 			 struct notes_merge_pair *changes, int *num_changes,
 			 struct notes_tree *t)
@@ -291,7 +320,7 @@ static int merge_changes(struct notes_merge_options *o,
 		} else {
 			/* need file-level merge between local and remote */
 			OUTPUT(o, 5, "\t\t\tneed content-level merge");
-			conflicts += 1; /* TODO */
+			conflicts += merge_one_change(o, p, t);
 		}
 	}
 
diff --git a/notes-merge.h b/notes-merge.h
index e42ce4b..e392049 100644
--- a/notes-merge.h
+++ b/notes-merge.h
@@ -6,6 +6,12 @@ struct notes_merge_options {
 	const char *remote_ref;
 	const char *commit_msg;
 	int verbosity;
+	enum {
+		NOTES_MERGE_RESOLVE_MANUAL = 0,
+		NOTES_MERGE_RESOLVE_OURS,
+		NOTES_MERGE_RESOLVE_THEIRS,
+		NOTES_MERGE_RESOLVE_UNION
+	} strategy;
 };
 
 void init_notes_merge_options(struct notes_merge_options *o);
diff --git a/t/t3309-notes-merge-auto-resolve.sh b/t/t3309-notes-merge-auto-resolve.sh
new file mode 100755
index 0000000..1a1fc7e
--- /dev/null
+++ b/t/t3309-notes-merge-auto-resolve.sh
@@ -0,0 +1,502 @@
+#!/bin/sh
+#
+# Copyright (c) 2010 Johan Herland
+#
+
+test_description='Test notes merging with auto-resolving strategies'
+
+. ./test-lib.sh
+
+# Set up a notes merge scenario with all kinds of potential conflicts
+test_expect_success 'setup commits' '
+	test_commit 1st &&
+	test_commit 2nd &&
+	test_commit 3rd &&
+	test_commit 4th &&
+	test_commit 5th &&
+	test_commit 6th &&
+	test_commit 7th &&
+	test_commit 8th &&
+	test_commit 9th &&
+	test_commit 10th &&
+	test_commit 11th &&
+	test_commit 12th &&
+	test_commit 13th &&
+	test_commit 14th &&
+	test_commit 15th
+'
+
+commit_sha1=$(git rev-parse 1st^{commit})
+commit_sha2=$(git rev-parse 2nd^{commit})
+commit_sha3=$(git rev-parse 3rd^{commit})
+commit_sha4=$(git rev-parse 4th^{commit})
+commit_sha5=$(git rev-parse 5th^{commit})
+commit_sha6=$(git rev-parse 6th^{commit})
+commit_sha7=$(git rev-parse 7th^{commit})
+commit_sha8=$(git rev-parse 8th^{commit})
+commit_sha9=$(git rev-parse 9th^{commit})
+commit_sha10=$(git rev-parse 10th^{commit})
+commit_sha11=$(git rev-parse 11th^{commit})
+commit_sha12=$(git rev-parse 12th^{commit})
+commit_sha13=$(git rev-parse 13th^{commit})
+commit_sha14=$(git rev-parse 14th^{commit})
+commit_sha15=$(git rev-parse 15th^{commit})
+
+verify_notes () {
+	notes_ref="$1"
+	suffix="$2"
+	git -c core.notesRef="refs/notes/$notes_ref" notes |
+		sort >"output_notes_$suffix" &&
+	test_cmp "expect_notes_$suffix" "output_notes_$suffix" &&
+	git -c core.notesRef="refs/notes/$notes_ref" log --format="%H %s%n%N" \
+		>"output_log_$suffix" &&
+	test_cmp "expect_log_$suffix" "output_log_$suffix"
+}
+
+test_expect_success 'setup merge base (x)' '
+	git config core.notesRef refs/notes/x &&
+	git notes add -m "x notes on 6th commit" 6th &&
+	git notes add -m "x notes on 7th commit" 7th &&
+	git notes add -m "x notes on 8th commit" 8th &&
+	git notes add -m "x notes on 9th commit" 9th &&
+	git notes add -m "x notes on 10th commit" 10th &&
+	git notes add -m "x notes on 11th commit" 11th &&
+	git notes add -m "x notes on 12th commit" 12th &&
+	git notes add -m "x notes on 13th commit" 13th &&
+	git notes add -m "x notes on 14th commit" 14th &&
+	git notes add -m "x notes on 15th commit" 15th
+'
+
+cat <<EOF | sort >expect_notes_x
+457a85d6c814ea208550f15fcc48f804ac8dc023 $commit_sha15
+b0c95b954301d69da2bc3723f4cb1680d355937c $commit_sha14
+5d30216a129eeffa97d9694ffe8c74317a560315 $commit_sha13
+dd161bc149470fd890dd4ab52a4cbd79bbd18c36 $commit_sha12
+7abbc45126d680336fb24294f013a7cdfa3ed545 $commit_sha11
+b8d03e173f67f6505a76f6e00cf93440200dd9be $commit_sha10
+20c613c835011c48a5abe29170a2402ca6354910 $commit_sha9
+a3daf8a1e4e5dc3409a303ad8481d57bfea7f5d6 $commit_sha8
+897003322b53bc6ca098e9324ee508362347e734 $commit_sha7
+11d97fdebfa5ceee540a3da07bce6fa0222bc082 $commit_sha6
+EOF
+
+cat >expect_log_x <<EOF
+$commit_sha15 15th
+x notes on 15th commit
+
+$commit_sha14 14th
+x notes on 14th commit
+
+$commit_sha13 13th
+x notes on 13th commit
+
+$commit_sha12 12th
+x notes on 12th commit
+
+$commit_sha11 11th
+x notes on 11th commit
+
+$commit_sha10 10th
+x notes on 10th commit
+
+$commit_sha9 9th
+x notes on 9th commit
+
+$commit_sha8 8th
+x notes on 8th commit
+
+$commit_sha7 7th
+x notes on 7th commit
+
+$commit_sha6 6th
+x notes on 6th commit
+
+$commit_sha5 5th
+
+$commit_sha4 4th
+
+$commit_sha3 3rd
+
+$commit_sha2 2nd
+
+$commit_sha1 1st
+
+EOF
+
+test_expect_success 'verify state of merge base (x)' 'verify_notes x x'
+
+test_expect_success 'setup local branch (y)' '
+	git update-ref refs/notes/y refs/notes/x &&
+	git config core.notesRef refs/notes/y &&
+	git notes add -f -m "y notes on 3rd commit" 3rd &&
+	git notes add -f -m "y notes on 4th commit" 4th &&
+	git notes add -f -m "y notes on 5th commit" 5th &&
+	git notes remove 6th &&
+	git notes remove 7th &&
+	git notes remove 8th &&
+	git notes add -f -m "y notes on 12th commit" 12th &&
+	git notes add -f -m "y notes on 13th commit" 13th &&
+	git notes add -f -m "y notes on 14th commit" 14th &&
+	git notes add -f -m "y notes on 15th commit" 15th
+'
+
+cat <<EOF | sort >expect_notes_y
+68b8630d25516028bed862719855b3d6768d7833 $commit_sha15
+5de7ea7ad4f47e7ff91989fb82234634730f75df $commit_sha14
+3a631fdb6f41b05b55d8f4baf20728ba8f6fccbc $commit_sha13
+a66055fa82f7a03fe0c02a6aba3287a85abf7c62 $commit_sha12
+7abbc45126d680336fb24294f013a7cdfa3ed545 $commit_sha11
+b8d03e173f67f6505a76f6e00cf93440200dd9be $commit_sha10
+20c613c835011c48a5abe29170a2402ca6354910 $commit_sha9
+154508c7a0bcad82b6fe4b472bc4c26b3bf0825b $commit_sha5
+e2bfd06a37dd2031684a59a6e2b033e212239c78 $commit_sha4
+5772f42408c0dd6f097a7ca2d24de0e78d1c46b1 $commit_sha3
+EOF
+
+cat >expect_log_y <<EOF
+$commit_sha15 15th
+y notes on 15th commit
+
+$commit_sha14 14th
+y notes on 14th commit
+
+$commit_sha13 13th
+y notes on 13th commit
+
+$commit_sha12 12th
+y notes on 12th commit
+
+$commit_sha11 11th
+x notes on 11th commit
+
+$commit_sha10 10th
+x notes on 10th commit
+
+$commit_sha9 9th
+x notes on 9th commit
+
+$commit_sha8 8th
+
+$commit_sha7 7th
+
+$commit_sha6 6th
+
+$commit_sha5 5th
+y notes on 5th commit
+
+$commit_sha4 4th
+y notes on 4th commit
+
+$commit_sha3 3rd
+y notes on 3rd commit
+
+$commit_sha2 2nd
+
+$commit_sha1 1st
+
+EOF
+
+test_expect_success 'verify state of local branch (y)' 'verify_notes y y'
+
+test_expect_success 'setup remote branch (z)' '
+	git update-ref refs/notes/z refs/notes/x &&
+	git config core.notesRef refs/notes/z &&
+	git notes add -f -m "z notes on 2nd commit" 2nd &&
+	git notes add -f -m "y notes on 4th commit" 4th &&
+	git notes add -f -m "z notes on 5th commit" 5th &&
+	git notes remove 6th &&
+	git notes add -f -m "z notes on 8th commit" 8th &&
+	git notes remove 9th &&
+	git notes add -f -m "z notes on 11th commit" 11th &&
+	git notes remove 12th &&
+	git notes add -f -m "y notes on 14th commit" 14th &&
+	git notes add -f -m "z notes on 15th commit" 15th
+'
+
+cat <<EOF | sort >expect_notes_z
+9b4b2c61f0615412da3c10f98ff85b57c04ec765 $commit_sha15
+5de7ea7ad4f47e7ff91989fb82234634730f75df $commit_sha14
+5d30216a129eeffa97d9694ffe8c74317a560315 $commit_sha13
+7e3c53503a3db8dd996cb62e37c66e070b44b54d $commit_sha11
+b8d03e173f67f6505a76f6e00cf93440200dd9be $commit_sha10
+851e1638784a884c7dd26c5d41f3340f6387413a $commit_sha8
+897003322b53bc6ca098e9324ee508362347e734 $commit_sha7
+99fc34adfc400b95c67b013115e37e31aa9a6d23 $commit_sha5
+e2bfd06a37dd2031684a59a6e2b033e212239c78 $commit_sha4
+283b48219aee9a4105f6cab337e789065c82c2b9 $commit_sha2
+EOF
+
+cat >expect_log_z <<EOF
+$commit_sha15 15th
+z notes on 15th commit
+
+$commit_sha14 14th
+y notes on 14th commit
+
+$commit_sha13 13th
+x notes on 13th commit
+
+$commit_sha12 12th
+
+$commit_sha11 11th
+z notes on 11th commit
+
+$commit_sha10 10th
+x notes on 10th commit
+
+$commit_sha9 9th
+
+$commit_sha8 8th
+z notes on 8th commit
+
+$commit_sha7 7th
+x notes on 7th commit
+
+$commit_sha6 6th
+
+$commit_sha5 5th
+z notes on 5th commit
+
+$commit_sha4 4th
+y notes on 4th commit
+
+$commit_sha3 3rd
+
+$commit_sha2 2nd
+z notes on 2nd commit
+
+$commit_sha1 1st
+
+EOF
+
+test_expect_success 'verify state of remote branch (z)' 'verify_notes z z'
+
+# At this point, before merging z into y, we have the following status:
+#
+# commit | base/x  | local/y | remote/z | diff from x to y/z         | result
+# -------|---------|---------|----------|----------------------------|-------
+# 1st    | [none]  | [none]  | [none]   | unchanged / unchanged      | [none]
+# 2nd    | [none]  | [none]  | 283b482  | unchanged / added          | 283b482
+# 3rd    | [none]  | 5772f42 | [none]   | added     / unchanged      | 5772f42
+# 4th    | [none]  | e2bfd06 | e2bfd06  | added     / added (same)   | e2bfd06
+# 5th    | [none]  | 154508c | 99fc34a  | added     / added (diff)   | ???
+# 6th    | 11d97fd | [none]  | [none]   | removed   / removed        | [none]
+# 7th    | 8970033 | [none]  | 8970033  | removed   / unchanged      | [none]
+# 8th    | a3daf8a | [none]  | 851e163  | removed   / changed        | ???
+# 9th    | 20c613c | 20c613c | [none]   | unchanged / removed        | [none]
+# 10th   | b8d03e1 | b8d03e1 | b8d03e1  | unchanged / unchanged      | b8d03e1
+# 11th   | 7abbc45 | 7abbc45 | 7e3c535  | unchanged / changed        | 7e3c535
+# 12th   | dd161bc | a66055f | [none]   | changed   / removed        | ???
+# 13th   | 5d30216 | 3a631fd | 5d30216  | changed   / unchanged      | 3a631fd
+# 14th   | b0c95b9 | 5de7ea7 | 5de7ea7  | changed   / changed (same) | 5de7ea7
+# 15th   | 457a85d | 68b8630 | 9b4b2c6  | changed   / changed (diff) | ???
+
+test_expect_success 'merge z into y with invalid strategy => Fail/No changes' '
+	git config core.notesRef refs/notes/y &&
+	test_must_fail git notes merge --strategy=foo z &&
+	# Verify no changes (y)
+	verify_notes y y
+'
+
+cat <<EOF | sort >expect_notes_ours
+68b8630d25516028bed862719855b3d6768d7833 $commit_sha15
+5de7ea7ad4f47e7ff91989fb82234634730f75df $commit_sha14
+3a631fdb6f41b05b55d8f4baf20728ba8f6fccbc $commit_sha13
+a66055fa82f7a03fe0c02a6aba3287a85abf7c62 $commit_sha12
+7e3c53503a3db8dd996cb62e37c66e070b44b54d $commit_sha11
+b8d03e173f67f6505a76f6e00cf93440200dd9be $commit_sha10
+154508c7a0bcad82b6fe4b472bc4c26b3bf0825b $commit_sha5
+e2bfd06a37dd2031684a59a6e2b033e212239c78 $commit_sha4
+5772f42408c0dd6f097a7ca2d24de0e78d1c46b1 $commit_sha3
+283b48219aee9a4105f6cab337e789065c82c2b9 $commit_sha2
+EOF
+
+cat >expect_log_ours <<EOF
+$commit_sha15 15th
+y notes on 15th commit
+
+$commit_sha14 14th
+y notes on 14th commit
+
+$commit_sha13 13th
+y notes on 13th commit
+
+$commit_sha12 12th
+y notes on 12th commit
+
+$commit_sha11 11th
+z notes on 11th commit
+
+$commit_sha10 10th
+x notes on 10th commit
+
+$commit_sha9 9th
+
+$commit_sha8 8th
+
+$commit_sha7 7th
+
+$commit_sha6 6th
+
+$commit_sha5 5th
+y notes on 5th commit
+
+$commit_sha4 4th
+y notes on 4th commit
+
+$commit_sha3 3rd
+y notes on 3rd commit
+
+$commit_sha2 2nd
+z notes on 2nd commit
+
+$commit_sha1 1st
+
+EOF
+
+test_expect_success 'merge z into y with "ours" strategy => Non-conflicting 3-way merge' '
+	git notes merge --strategy=ours z &&
+	verify_notes y ours
+'
+
+test_expect_success 'reset to pre-merge state (y)' '
+	git update-ref refs/notes/y refs/notes/y^1 &&
+	# Verify pre-merge state
+	verify_notes y y
+'
+
+cat <<EOF | sort >expect_notes_theirs
+9b4b2c61f0615412da3c10f98ff85b57c04ec765 $commit_sha15
+5de7ea7ad4f47e7ff91989fb82234634730f75df $commit_sha14
+3a631fdb6f41b05b55d8f4baf20728ba8f6fccbc $commit_sha13
+7e3c53503a3db8dd996cb62e37c66e070b44b54d $commit_sha11
+b8d03e173f67f6505a76f6e00cf93440200dd9be $commit_sha10
+851e1638784a884c7dd26c5d41f3340f6387413a $commit_sha8
+99fc34adfc400b95c67b013115e37e31aa9a6d23 $commit_sha5
+e2bfd06a37dd2031684a59a6e2b033e212239c78 $commit_sha4
+5772f42408c0dd6f097a7ca2d24de0e78d1c46b1 $commit_sha3
+283b48219aee9a4105f6cab337e789065c82c2b9 $commit_sha2
+EOF
+
+cat >expect_log_theirs <<EOF
+$commit_sha15 15th
+z notes on 15th commit
+
+$commit_sha14 14th
+y notes on 14th commit
+
+$commit_sha13 13th
+y notes on 13th commit
+
+$commit_sha12 12th
+
+$commit_sha11 11th
+z notes on 11th commit
+
+$commit_sha10 10th
+x notes on 10th commit
+
+$commit_sha9 9th
+
+$commit_sha8 8th
+z notes on 8th commit
+
+$commit_sha7 7th
+
+$commit_sha6 6th
+
+$commit_sha5 5th
+z notes on 5th commit
+
+$commit_sha4 4th
+y notes on 4th commit
+
+$commit_sha3 3rd
+y notes on 3rd commit
+
+$commit_sha2 2nd
+z notes on 2nd commit
+
+$commit_sha1 1st
+
+EOF
+
+test_expect_success 'merge z into y with "theirs" strategy => Non-conflicting 3-way merge' '
+	git notes merge --strategy=theirs z &&
+	verify_notes y theirs
+'
+
+test_expect_success 'reset to pre-merge state (y)' '
+	git update-ref refs/notes/y refs/notes/y^1 &&
+	# Verify pre-merge state
+	verify_notes y y
+'
+
+cat <<EOF | sort >expect_notes_union
+7c4e546efd0fe939f876beb262ece02797880b54 $commit_sha15
+5de7ea7ad4f47e7ff91989fb82234634730f75df $commit_sha14
+3a631fdb6f41b05b55d8f4baf20728ba8f6fccbc $commit_sha13
+a66055fa82f7a03fe0c02a6aba3287a85abf7c62 $commit_sha12
+7e3c53503a3db8dd996cb62e37c66e070b44b54d $commit_sha11
+b8d03e173f67f6505a76f6e00cf93440200dd9be $commit_sha10
+851e1638784a884c7dd26c5d41f3340f6387413a $commit_sha8
+6c841cc36ea496027290967ca96bd2bef54dbb47 $commit_sha5
+e2bfd06a37dd2031684a59a6e2b033e212239c78 $commit_sha4
+5772f42408c0dd6f097a7ca2d24de0e78d1c46b1 $commit_sha3
+283b48219aee9a4105f6cab337e789065c82c2b9 $commit_sha2
+EOF
+
+cat >expect_log_union <<EOF
+$commit_sha15 15th
+y notes on 15th commit
+
+z notes on 15th commit
+
+$commit_sha14 14th
+y notes on 14th commit
+
+$commit_sha13 13th
+y notes on 13th commit
+
+$commit_sha12 12th
+y notes on 12th commit
+
+$commit_sha11 11th
+z notes on 11th commit
+
+$commit_sha10 10th
+x notes on 10th commit
+
+$commit_sha9 9th
+
+$commit_sha8 8th
+z notes on 8th commit
+
+$commit_sha7 7th
+
+$commit_sha6 6th
+
+$commit_sha5 5th
+y notes on 5th commit
+
+z notes on 5th commit
+
+$commit_sha4 4th
+y notes on 4th commit
+
+$commit_sha3 3rd
+y notes on 3rd commit
+
+$commit_sha2 2nd
+z notes on 2nd commit
+
+$commit_sha1 1st
+
+EOF
+
+test_expect_success 'merge z into y with "union" strategy => Non-conflicting 3-way merge' '
+	git notes merge --strategy=union z &&
+	verify_notes y union
+'
+
+test_done
-- 
1.7.3.98.g5ad7d9

[PATCH 12/18] Documentation: Preliminary docs on 'git notes merge'

[Johan Herland]

This patch has been improved by the following contributions:
- Stephen Boyd: Use "automatically resolves" instead of "auto-resolves"

Cc: Stephen Boyd <bebarino@gmail.com>
Signed-off-by: Johan Herland <johan@herland.net>
---
 Documentation/git-notes.txt |   44 ++++++++++++++++++++++++++++++++++++++++++-
 1 files changed, 43 insertions(+), 1 deletions(-)

diff --git a/Documentation/git-notes.txt b/Documentation/git-notes.txt
index 2981d8c..b9a061c 100644
--- a/Documentation/git-notes.txt
+++ b/Documentation/git-notes.txt
@@ -14,6 +14,7 @@ SYNOPSIS
 'git notes' append [-F <file> | -m <msg> | (-c | -C) <object>] [<object>]
 'git notes' edit [<object>]
 'git notes' show [<object>]
+'git notes' merge [-v | -q] [-s <strategy> ] <notes_ref>
 'git notes' remove [<object>]
 'git notes' prune [-n | -v]
 
@@ -83,6 +84,16 @@ edit::
 show::
 	Show the notes for a given object (defaults to HEAD).
 
+merge::
+	Merge the given notes ref into the current notes ref.
+	This will try to merge the changes made by the given
+	notes ref (called "remote") since the merge-base (if
+	any) into the current notes ref (called "local").
++
+If conflicts arise (and a strategy for automatically resolving
+conflicting notes (see the -s/--strategy option) is not given,
+the merge fails (TODO).
+
 remove::
 	Remove the notes for a given object (defaults to HEAD).
 	This is equivalent to specifying an empty note message to
@@ -133,9 +144,23 @@ OPTIONS
 	Do not remove anything; just report the object names whose notes
 	would be removed.
 
+-s <strategy>::
+--strategy=<strategy>::
+	When merging notes, resolve notes conflicts using the given
+	strategy. The following strategies are recognized: "manual"
+	(default), "ours", "theirs" and "union".
+	See the "NOTES MERGE STRATEGIES" section below for more
+	information on each notes merge strategy.
+
+-q::
+--quiet::
+	When merging notes, operate quietly.
+
 -v::
 --verbose::
-	Report all object names whose notes are removed.
+	When merging notes, be more verbose.
+	When pruning notes, report all object names whose notes are
+	removed.
 
 
 DISCUSSION
@@ -163,6 +188,23 @@ object, in which case the history of the notes can be read with
 `git log -p -g <refname>`.
 
 
+NOTES MERGE STRATEGIES
+----------------------
+
+The default notes merge strategy is "manual", which is not yet
+implemented (TODO).
+
+"ours" automatically resolves conflicting notes in favor of the local
+version (i.e. the current notes ref).
+
+"theirs" automatically resolves notes conflicts in favor of the remote
+version (i.e. the given notes ref being merged into the current notes
+ref).
+
+"union" automatically resolves notes conflicts by concatenating the
+local and remote versions.
+
+
 EXAMPLES
 --------
 
-- 
1.7.3.98.g5ad7d9

[PATCH 13/18] git notes merge: Manual conflict resolution, part 1/2

[Johan Herland]

Conflicts (that are to be resolved manually) are written into a special-
purpose working tree, located at .git/NOTES_MERGE_WORKTREE. Within this
directory, conflicting notes entries are stored (with conflict markers
produced by ll_merge()) using the SHA1 of the annotated object. The
.git/NOTES_MERGE_WORKTREE directory will only contain the _conflicting_
note entries. The non-conflicting note entries (aka. the partial merge
result) are stored in 'local_tree', and the SHA1 of the resulting commit
is written to 'result_sha1'. The return value from notes_merge() is -1.

The user is told to edit the files within the .git/NOTES_MERGE_WORKTREE
directory in order to resolve the conflicts.

The patch also contains documentation and testcases for the correct setup
of .git/NOTES_MERGE_WORKTREE.

The next part will recombine the partial notes merge result with the
resolved conflicts in .git/NOTES_MERGE_WORKTREE to produce the complete
merge result.

Signed-off-by: Johan Herland <johan@herland.net>
---
 Documentation/git-notes.txt           |   10 +-
 builtin/notes.c                       |    8 +-
 notes-merge.c                         |  166 ++++++++++++++++++-
 notes-merge.h                         |   11 +-
 t/t3310-notes-merge-manual-resolve.sh |  292 +++++++++++++++++++++++++++++++++
 5 files changed, 474 insertions(+), 13 deletions(-)
 create mode 100755 t/t3310-notes-merge-manual-resolve.sh

diff --git a/Documentation/git-notes.txt b/Documentation/git-notes.txt
index b9a061c..12fda54 100644
--- a/Documentation/git-notes.txt
+++ b/Documentation/git-notes.txt
@@ -92,7 +92,9 @@ merge::
 +
 If conflicts arise (and a strategy for automatically resolving
 conflicting notes (see the -s/--strategy option) is not given,
-the merge fails (TODO).
+the "manual" resolver is used. This resolver checks out the
+conflicting notes in a special worktree (`.git/NOTES_MERGE_WORKTREE`),
+and instructs the user to manually resolve the conflicts there.
 
 remove::
 	Remove the notes for a given object (defaults to HEAD).
@@ -191,8 +193,10 @@ object, in which case the history of the notes can be read with
 NOTES MERGE STRATEGIES
 ----------------------
 
-The default notes merge strategy is "manual", which is not yet
-implemented (TODO).
+The default notes merge strategy is "manual", which checks out
+conflicting notes in a special work tree for resolving notes conflicts
+(`.git/NOTES_MERGE_WORKTREE`), and instructs the user to resolve the
+conflicts in that work tree.
 
 "ours" automatically resolves conflicting notes in favor of the local
 version (i.e. the current notes ref).
diff --git a/builtin/notes.c b/builtin/notes.c
index 79290db..b1f3ae6 100644
--- a/builtin/notes.c
+++ b/builtin/notes.c
@@ -819,14 +819,14 @@ static int merge(int argc, const char **argv, const char *prefix)
 		/* Update default notes ref with new commit */
 		update_ref(msg.buf, default_notes_ref(), result_sha1, NULL,
 			   0, DIE_ON_ERR);
-	else
-		/* TODO: */
-		die("'git notes merge' cannot yet handle conflicts!");
+	else /* Merge has unresolved conflicts */
+		printf("Automatic notes merge failed. Fix conflicts in %s.\n",
+		       git_path(NOTES_MERGE_WORKTREE));
 
 	free_notes(t);
 	strbuf_release(&remote_ref);
 	strbuf_release(&msg);
-	return 0;
+	return result < 0; /* return non-zero on conflicts */
 }
 
 static int remove_cmd(int argc, const char **argv, const char *prefix)
diff --git a/notes-merge.c b/notes-merge.c
index 6fa59d8..8efa003 100644
--- a/notes-merge.c
+++ b/notes-merge.c
@@ -2,6 +2,9 @@
 #include "commit.h"
 #include "diff.h"
 #include "diffcore.h"
+#include "xdiff-interface.h"
+#include "ll-merge.h"
+#include "dir.h"
 #include "notes.h"
 #include "notes-merge.h"
 
@@ -262,16 +265,169 @@ static void diff_tree_local(struct notes_merge_options *o,
 	diff_tree_release_paths(&opt);
 }
 
+static void check_notes_merge_worktree(struct notes_merge_options *o)
+{
+	if (!o->has_worktree) {
+		/*
+		 * Must establish NOTES_MERGE_WORKTREE.
+		 * Abort if NOTES_MERGE_WORKTREE already exists
+		 */
+		if (file_exists(git_path(NOTES_MERGE_WORKTREE))) {
+			if (advice_resolve_conflict)
+				die("You have not concluded your previous "
+				    "notes merge (%s exists).\nPlease, use "
+				    "'git notes merge --commit' or 'git notes "
+				    "merge --reset' to commit/abort the "
+				    "previous merge before you start a new "
+				    "notes merge.", git_path("NOTES_MERGE_*"));
+			else
+				die("You have not concluded your notes merge "
+				    "(%s exists).", git_path("NOTES_MERGE_*"));
+		}
+
+		if (safe_create_leading_directories(git_path(
+				NOTES_MERGE_WORKTREE "/.test")))
+			die_errno("unable to create directory %s",
+				  git_path(NOTES_MERGE_WORKTREE));
+		o->has_worktree = 1;
+	} else if (!file_exists(git_path(NOTES_MERGE_WORKTREE)))
+		/* NOTES_MERGE_WORKTREE should already be established */
+		die("missing '%s'. This should not happen",
+		    git_path(NOTES_MERGE_WORKTREE));
+}
+
+static void write_buf_to_worktree(const unsigned char *obj,
+				  void *buf, unsigned long size)
+{
+	int fd;
+	char *path = git_path(NOTES_MERGE_WORKTREE "/%s", sha1_to_hex(obj));
+	if (safe_create_leading_directories(path))
+		die_errno("unable to create directory for '%s'", path);
+	if (file_exists(path))
+		die("found existing file at '%s'", path);
+
+	fd = open(path, O_WRONLY | O_TRUNC | O_CREAT, 0666);
+	if (fd < 0)
+		die_errno("failed to open '%s'", path);
+
+	while (size > 0) {
+		long ret = write_in_full(fd, buf, size);
+		if (ret < 0) {
+			/* Ignore epipe */
+			if (errno == EPIPE)
+				break;
+			die_errno("notes-merge");
+		} else if (!ret) {
+			die("notes-merge: disk full?");
+		}
+		size -= ret;
+		buf += ret;
+	}
+
+	close(fd);
+}
+
+static void write_note_to_worktree(const unsigned char *obj,
+				   const unsigned char *note)
+{
+	enum object_type type;
+	unsigned long size;
+	void *buf = read_sha1_file(note, &type, &size);
+
+	if (!buf)
+		die("cannot read note %s for object %s",
+		    sha1_to_hex(note), sha1_to_hex(obj));
+	if (type != OBJ_BLOB)
+		die("blob expected in note %s for object %s",
+		    sha1_to_hex(note), sha1_to_hex(obj));
+	write_buf_to_worktree(obj, buf, size);
+	free(buf);
+}
+
+static int ll_merge_in_worktree(struct notes_merge_options *o,
+				struct notes_merge_pair *p)
+{
+	mmbuffer_t result_buf;
+	mmfile_t base, local, remote;
+	int status;
+
+	read_mmblob(&base, p->base);
+	read_mmblob(&local, p->local);
+	read_mmblob(&remote, p->remote);
+
+	status = ll_merge(&result_buf, sha1_to_hex(p->obj), &base, NULL,
+			  &local, o->local_ref, &remote, o->remote_ref, 0);
+
+	free(base.ptr);
+	free(local.ptr);
+	free(remote.ptr);
+
+	if ((status < 0) || !result_buf.ptr)
+		die("Failed to execute internal merge");
+
+	write_buf_to_worktree(p->obj, result_buf.ptr, result_buf.size);
+	free(result_buf.ptr);
+
+	return status;
+}
+
+static int merge_one_change_manual(struct notes_merge_options *o,
+				   struct notes_merge_pair *p,
+				   struct notes_tree *t)
+{
+	const char *lref = o->local_ref ? o->local_ref : "local version";
+	const char *rref = o->remote_ref ? o->remote_ref : "remote version";
+
+	OUTPUT(o, 5, "\t\t\tmerge_one_change_manual(obj = %.7s, base = %.7s, "
+	       "local = %.7s, remote = %.7s)",
+	       sha1_to_hex(p->obj), sha1_to_hex(p->base),
+	       sha1_to_hex(p->local), sha1_to_hex(p->remote));
+
+	OUTPUT(o, 2, "Auto-merging notes for %s", sha1_to_hex(p->obj));
+	check_notes_merge_worktree(o);
+	if (is_null_sha1(p->local)) {
+		/* D/F conflict, checkout p->remote */
+		assert(!is_null_sha1(p->remote));
+		OUTPUT(o, 1, "CONFLICT (delete/modify): Notes for object %s "
+		       "deleted in %s and modified in %s. Version from %s "
+		       "left in tree.", sha1_to_hex(p->obj), lref, rref, rref);
+		write_note_to_worktree(p->obj, p->remote);
+	} else if (is_null_sha1(p->remote)) {
+		/* D/F conflict, checkout p->local */
+		assert(!is_null_sha1(p->local));
+		OUTPUT(o, 1, "CONFLICT (delete/modify): Notes for object %s "
+		       "deleted in %s and modified in %s. Version from %s "
+		       "left in tree.", sha1_to_hex(p->obj), rref, lref, lref);
+		write_note_to_worktree(p->obj, p->local);
+	} else {
+		/* "regular" conflict, checkout result of ll_merge() */
+		const char *reason = "content";
+		if (is_null_sha1(p->base))
+			reason = "add/add";
+		assert(!is_null_sha1(p->local));
+		assert(!is_null_sha1(p->remote));
+		OUTPUT(o, 1, "CONFLICT (%s): Merge conflict in notes for "
+		       "object %s", reason, sha1_to_hex(p->obj));
+		ll_merge_in_worktree(o, p);
+	}
+
+	OUTPUT(o, 5, "\t\t\tremoving from partial merge result");
+	remove_note(t, p->obj);
+
+	return 1;
+}
+
 static int merge_one_change(struct notes_merge_options *o,
 			    struct notes_merge_pair *p, struct notes_tree *t)
 {
 	/*
-	 * Return 0 if change was resolved (and added to notes_tree),
-	 * 1 if conflict
+	 * Return 0 if change is successfully resolved (stored in notes_tree).
+	 * Return 1 is change results in a conflict (NOT stored in notes_tree,
+	 * but instead written to NOTES_MERGE_WORKTREE with conflict markers).
 	 */
 	switch (o->strategy) {
 	case NOTES_MERGE_RESOLVE_MANUAL:
-		return 1;
+		return merge_one_change_manual(o, p, t);
 	case NOTES_MERGE_RESOLVE_OURS:
 		OUTPUT(o, 2, "Using local notes for %s", sha1_to_hex(p->obj));
 		/* nothing to do */
@@ -461,8 +617,8 @@ int notes_merge(struct notes_merge_options *o,
 	result = merge_from_diffs(o, base_tree_sha1, local->tree->object.sha1,
 				  remote->tree->object.sha1, local_tree);
 
-	if (result > 0) { /* successful non-trivial merge */
-		/* Commit result */
+	if (result != 0) { /* non-trivial merge (with or without conflicts) */
+		/* Commit (partial) result */
 		struct commit_list *parents = NULL;
 		commit_list_insert(remote, &parents); /* LIFO order */
 		commit_list_insert(local, &parents);
diff --git a/notes-merge.h b/notes-merge.h
index e392049..e9a8ce6 100644
--- a/notes-merge.h
+++ b/notes-merge.h
@@ -1,6 +1,8 @@
 #ifndef NOTES_MERGE_H
 #define NOTES_MERGE_H
 
+#define NOTES_MERGE_WORKTREE "NOTES_MERGE_WORKTREE"
+
 struct notes_merge_options {
 	const char *local_ref;
 	const char *remote_ref;
@@ -12,6 +14,7 @@ struct notes_merge_options {
 		NOTES_MERGE_RESOLVE_THEIRS,
 		NOTES_MERGE_RESOLVE_UNION
 	} strategy;
+	unsigned has_worktree:1;
 };
 
 void init_notes_merge_options(struct notes_merge_options *o);
@@ -46,7 +49,13 @@ void create_notes_commit(struct notes_tree *t, struct commit_list *parents,
  * 2. The merge successfully completes, producing a merge commit. local_tree
  *    contains the updated notes tree, the SHA1 of the resulting commit is
  *    written into 'result_sha1', and 1 is returned.
- * 3. The merge fails. result_sha1 is set to null_sha1, and -1 is returned.
+ * 3. The merge results in conflicts. This is similar to #2 in that the
+ *    partial merge result (i.e. merge result minus the unmerged entries)
+ *    are stored in 'local_tree', and the SHA1 or the resulting commit
+ *    (to be amended when the conflicts have been resolved) is written into
+ *    'result_sha1'. The unmerged entries are written into the
+ *    .git/NOTES_MERGE_WORKTREE directory with conflict markers.
+ *    -1 is returned.
  *
  * Either ref (but not both) may not exist in which case the missing ref is
  * interpreted as an empty notes tree, and the merge trivially results in
diff --git a/t/t3310-notes-merge-manual-resolve.sh b/t/t3310-notes-merge-manual-resolve.sh
new file mode 100755
index 0000000..eadb6b7
--- /dev/null
+++ b/t/t3310-notes-merge-manual-resolve.sh
@@ -0,0 +1,292 @@
+#!/bin/sh
+#
+# Copyright (c) 2010 Johan Herland
+#
+
+test_description='Test notes merging with manual conflict resolution'
+
+. ./test-lib.sh
+
+# Set up a notes merge scenario with different kinds of conflicts
+test_expect_success 'setup commits' '
+	test_commit 1st &&
+	test_commit 2nd &&
+	test_commit 3rd &&
+	test_commit 4th &&
+	test_commit 5th
+'
+
+commit_sha1=$(git rev-parse 1st^{commit})
+commit_sha2=$(git rev-parse 2nd^{commit})
+commit_sha3=$(git rev-parse 3rd^{commit})
+commit_sha4=$(git rev-parse 4th^{commit})
+commit_sha5=$(git rev-parse 5th^{commit})
+
+verify_notes () {
+	notes_ref="$1"
+	git -c core.notesRef="refs/notes/$notes_ref" notes |
+		sort >"output_notes_$notes_ref" &&
+	test_cmp "expect_notes_$notes_ref" "output_notes_$notes_ref" &&
+	git -c core.notesRef="refs/notes/$notes_ref" log --format="%H %s%n%N" \
+		>"output_log_$notes_ref" &&
+	test_cmp "expect_log_$notes_ref" "output_log_$notes_ref"
+}
+
+cat <<EOF | sort >expect_notes_x
+6e8e3febca3c2bb896704335cc4d0c34cb2f8715 $commit_sha4
+e5388c10860456ee60673025345fe2e153eb8cf8 $commit_sha3
+ceefa674873670e7ecd131814d909723cce2b669 $commit_sha2
+EOF
+
+cat >expect_log_x <<EOF
+$commit_sha5 5th
+
+$commit_sha4 4th
+x notes on 4th commit
+
+$commit_sha3 3rd
+x notes on 3rd commit
+
+$commit_sha2 2nd
+x notes on 2nd commit
+
+$commit_sha1 1st
+
+EOF
+
+test_expect_success 'setup merge base (x)' '
+	git config core.notesRef refs/notes/x &&
+	git notes add -m "x notes on 2nd commit" 2nd &&
+	git notes add -m "x notes on 3rd commit" 3rd &&
+	git notes add -m "x notes on 4th commit" 4th &&
+	verify_notes x
+'
+
+cat <<EOF | sort >expect_notes_y
+e2bfd06a37dd2031684a59a6e2b033e212239c78 $commit_sha4
+5772f42408c0dd6f097a7ca2d24de0e78d1c46b1 $commit_sha3
+b0a6021ec006d07e80e9b20ec9b444cbd9d560d3 $commit_sha1
+EOF
+
+cat >expect_log_y <<EOF
+$commit_sha5 5th
+
+$commit_sha4 4th
+y notes on 4th commit
+
+$commit_sha3 3rd
+y notes on 3rd commit
+
+$commit_sha2 2nd
+
+$commit_sha1 1st
+y notes on 1st commit
+
+EOF
+
+test_expect_success 'setup local branch (y)' '
+	git update-ref refs/notes/y refs/notes/x &&
+	git config core.notesRef refs/notes/y &&
+	git notes add -f -m "y notes on 1st commit" 1st &&
+	git notes remove 2nd &&
+	git notes add -f -m "y notes on 3rd commit" 3rd &&
+	git notes add -f -m "y notes on 4th commit" 4th &&
+	verify_notes y
+'
+
+cat <<EOF | sort >expect_notes_z
+cff59c793c20bb49a4e01bc06fb06bad642e0d54 $commit_sha4
+283b48219aee9a4105f6cab337e789065c82c2b9 $commit_sha2
+0a81da8956346e19bcb27a906f04af327e03e31b $commit_sha1
+EOF
+
+cat >expect_log_z <<EOF
+$commit_sha5 5th
+
+$commit_sha4 4th
+z notes on 4th commit
+
+$commit_sha3 3rd
+
+$commit_sha2 2nd
+z notes on 2nd commit
+
+$commit_sha1 1st
+z notes on 1st commit
+
+EOF
+
+test_expect_success 'setup remote branch (z)' '
+	git update-ref refs/notes/z refs/notes/x &&
+	git config core.notesRef refs/notes/z &&
+	git notes add -f -m "z notes on 1st commit" 1st &&
+	git notes add -f -m "z notes on 2nd commit" 2nd &&
+	git notes remove 3rd &&
+	git notes add -f -m "z notes on 4th commit" 4th &&
+	verify_notes z
+'
+
+# At this point, before merging z into y, we have the following status:
+#
+# commit | base/x  | local/y | remote/z | diff from x to y/z
+# -------|---------|---------|----------|---------------------------
+# 1st    | [none]  | b0a6021 | 0a81da8  | added     / added (diff)
+# 2nd    | ceefa67 | [none]  | 283b482  | removed   / changed
+# 3rd    | e5388c1 | 5772f42 | [none]   | changed   / removed
+# 4th    | 6e8e3fe | e2bfd06 | cff59c7  | changed   / changed (diff)
+# 5th    | [none]  | [none]  | [none]   | [none]
+
+cat <<EOF | sort >expect_conflicts
+$commit_sha1
+$commit_sha2
+$commit_sha3
+$commit_sha4
+EOF
+
+cat >expect_conflict_$commit_sha1 <<EOF
+<<<<<<< refs/notes/m
+y notes on 1st commit
+=======
+z notes on 1st commit
+>>>>>>> refs/notes/z
+EOF
+
+cat >expect_conflict_$commit_sha2 <<EOF
+z notes on 2nd commit
+EOF
+
+cat >expect_conflict_$commit_sha3 <<EOF
+y notes on 3rd commit
+EOF
+
+cat >expect_conflict_$commit_sha4 <<EOF
+<<<<<<< refs/notes/m
+y notes on 4th commit
+=======
+z notes on 4th commit
+>>>>>>> refs/notes/z
+EOF
+
+cp expect_notes_y expect_notes_m
+cp expect_log_y expect_log_m
+
+git rev-parse refs/notes/y > pre_merge_y
+
+test_expect_success 'merge z into m (== y) with default ("manual") resolver => Conflicting 3-way merge' '
+	git update-ref refs/notes/m refs/notes/y &&
+	git config core.notesRef refs/notes/m &&
+	test_must_fail git notes merge z >output &&
+	# Output should point to where to resolve conflicts
+	grep -q "\\.git/NOTES_MERGE_WORKTREE" output &&
+	# Inspect merge conflicts
+	ls .git/NOTES_MERGE_WORKTREE >output_conflicts &&
+	test_cmp expect_conflicts output_conflicts &&
+	( for f in $(cat expect_conflicts); do
+		test_cmp "expect_conflict_$f" ".git/NOTES_MERGE_WORKTREE/$f" ||
+		exit 1
+	done ) &&
+	# Verify that current notes tree (pre-merge) has not changed (m == y)
+	verify_notes y &&
+	verify_notes m &&
+	test "$(git rev-parse refs/notes/m)" = "$(cat pre_merge_y)"
+'
+
+cat <<EOF | sort >expect_notes_z
+00494adecf2d9635a02fa431308d67993f853968 $commit_sha4
+283b48219aee9a4105f6cab337e789065c82c2b9 $commit_sha2
+0a81da8956346e19bcb27a906f04af327e03e31b $commit_sha1
+EOF
+
+cat >expect_log_z <<EOF
+$commit_sha5 5th
+
+$commit_sha4 4th
+z notes on 4th commit
+
+More z notes on 4th commit
+
+$commit_sha3 3rd
+
+$commit_sha2 2nd
+z notes on 2nd commit
+
+$commit_sha1 1st
+z notes on 1st commit
+
+EOF
+
+test_expect_success 'change notes in z' '
+	git notes --ref z append -m "More z notes on 4th commit" 4th &&
+	verify_notes z
+'
+
+test_expect_success 'cannot do merge w/conflicts when previous merge is unfinished' '
+	test -d .git/NOTES_MERGE_WORKTREE &&
+	test_must_fail git notes merge z >output 2>&1 &&
+	# Output should indicate what is wrong
+	grep -q "\\.git/NOTES_MERGE_\\* exists" output
+'
+
+# Setup non-conflicting merge between x and new notes ref w
+
+cat <<EOF | sort >expect_notes_w
+ceefa674873670e7ecd131814d909723cce2b669 $commit_sha2
+f75d1df88cbfe4258d49852f26cfc83f2ad4494b $commit_sha1
+EOF
+
+cat >expect_log_w <<EOF
+$commit_sha5 5th
+
+$commit_sha4 4th
+
+$commit_sha3 3rd
+
+$commit_sha2 2nd
+x notes on 2nd commit
+
+$commit_sha1 1st
+w notes on 1st commit
+
+EOF
+
+test_expect_success 'setup unrelated notes ref (w)' '
+	git config core.notesRef refs/notes/w &&
+	git notes add -m "w notes on 1st commit" 1st &&
+	git notes add -m "x notes on 2nd commit" 2nd &&
+	verify_notes w
+'
+
+cat <<EOF | sort >expect_notes_w
+6e8e3febca3c2bb896704335cc4d0c34cb2f8715 $commit_sha4
+e5388c10860456ee60673025345fe2e153eb8cf8 $commit_sha3
+ceefa674873670e7ecd131814d909723cce2b669 $commit_sha2
+f75d1df88cbfe4258d49852f26cfc83f2ad4494b $commit_sha1
+EOF
+
+cat >expect_log_w <<EOF
+$commit_sha5 5th
+
+$commit_sha4 4th
+x notes on 4th commit
+
+$commit_sha3 3rd
+x notes on 3rd commit
+
+$commit_sha2 2nd
+x notes on 2nd commit
+
+$commit_sha1 1st
+w notes on 1st commit
+
+EOF
+
+test_expect_success 'can do merge without conflicts even if previous merge is unfinished (x => w)' '
+	test -d .git/NOTES_MERGE_WORKTREE &&
+	git notes merge x &&
+	verify_notes w &&
+	# Verify that other notes refs has not changed (x and y)
+	verify_notes x &&
+	verify_notes y
+'
+
+test_done
-- 
1.7.3.98.g5ad7d9

[PATCH 14/18] git notes merge: Manual conflict resolution, part 2/2

[Johan Herland]

When the notes merge conflicts in .git/NOTES_MERGE_WORKTREE have been
resolved, we need to record a new notes commit on the appropriate notes
ref with the resolved notes.

This patch implements 'git notes merge --commit' which the user should
run after resolving conflicts in the notes merge worktree. This command
finalizes the notes merge by recombining the partial notes tree from
part 1 with the now-resolved conflicts in the notes merge worktree in a
merge commit, and updating the appropriate ref to this merge commit.

In order to correctly finalize the merge, we need to keep track of three
things:

- The partial merge result from part 1, containing the auto-merged notes.
  This is now stored into a ref called .git/NOTES_MERGE_PARTIAL.
- The unmerged notes. These are already stored in
  .git/NOTES_MERGE_WORKTREE, thanks to part 1.
- The notes ref to be updated by the finalized merge result. This is now
  stored in a symref called .git/NOTES_MERGE_REF.

In addition to "git notes merge --commit", which uses the above details
to create the finalized notes merge commit, this patch also implements
"git notes merge --reset", which aborts the ongoing notes merge by simply
removing the files/directory described above.

FTR, "git notes merge --commit" reuses "git notes merge --reset" to remove
the information described above (.git/NOTES_MERGE_*) after the notes merge
have been successfully finalized.

The patch also contains documentation and testcases for the two new options.

Signed-off-by: Johan Herland <johan@herland.net>
---
 Documentation/git-notes.txt           |   23 +++++
 builtin/notes.c                       |  107 +++++++++++++++++++-
 notes-merge.c                         |   69 +++++++++++++
 notes-merge.h                         |   23 +++++
 t/t3310-notes-merge-manual-resolve.sh |  176 +++++++++++++++++++++++++++++++++
 5 files changed, 395 insertions(+), 3 deletions(-)

diff --git a/Documentation/git-notes.txt b/Documentation/git-notes.txt
index 12fda54..ede7755 100644
--- a/Documentation/git-notes.txt
+++ b/Documentation/git-notes.txt
@@ -15,6 +15,8 @@ SYNOPSIS
 'git notes' edit [<object>]
 'git notes' show [<object>]
 'git notes' merge [-v | -q] [-s <strategy> ] <notes_ref>
+'git notes' merge --commit [-v | -q]
+'git notes' merge --reset [-v | -q]
 'git notes' remove [<object>]
 'git notes' prune [-n | -v]
 
@@ -95,6 +97,9 @@ conflicting notes (see the -s/--strategy option) is not given,
 the "manual" resolver is used. This resolver checks out the
 conflicting notes in a special worktree (`.git/NOTES_MERGE_WORKTREE`),
 and instructs the user to manually resolve the conflicts there.
+When done, the user can either finalize the merge with
+'git notes merge --commit', or abort the merge with
+'git notes merge --reset'.
 
 remove::
 	Remove the notes for a given object (defaults to HEAD).
@@ -154,6 +159,21 @@ OPTIONS
 	See the "NOTES MERGE STRATEGIES" section below for more
 	information on each notes merge strategy.
 
+--commit::
+	Finalize an in-progress 'git notes merge', i.e. a notes merge with
+	conflicts. When 'git notes merge' encounters conflicts, it s
+	which returned one or more conflicts (that you have now resolved)
+	in .git/NOTES_MERGE_WORKTREE. This amends the partial merge commit
+	created by 'git notes merge' (stored in .git/NOTES_MERGE_PARTIAL)
+	by adding the notes in .git/NOTES_MERGE_WORKTREE. The notes ref
+	stored in the .git/NOTES_MERGE_REF symref is updated to the
+	resulting commit.
+
+--reset::
+	Reset/abort a in-progress 'git notes merge', i.e. a notes merge
+	with conflicts. This simply removes all files related to the
+	notes merge.
+
 -q::
 --quiet::
 	When merging notes, operate quietly.
@@ -197,6 +217,9 @@ The default notes merge strategy is "manual", which checks out
 conflicting notes in a special work tree for resolving notes conflicts
 (`.git/NOTES_MERGE_WORKTREE`), and instructs the user to resolve the
 conflicts in that work tree.
+When done, the user can either finalize the merge with
+'git notes merge --commit', or abort the merge with
+'git notes merge --reset'.
 
 "ours" automatically resolves conflicting notes in favor of the local
 version (i.e. the current notes ref).
diff --git a/builtin/notes.c b/builtin/notes.c
index b1f3ae6..8be7d9e 100644
--- a/builtin/notes.c
+++ b/builtin/notes.c
@@ -27,6 +27,8 @@ static const char * const git_notes_usage[] = {
 	"git notes [--ref <notes_ref>] edit [<object>]",
 	"git notes [--ref <notes_ref>] show [<object>]",
 	"git notes [--ref <notes_ref>] merge [-v | -q] [-s <strategy> ] <notes_ref>",
+	"git notes merge --commit [-v | -q]",
+	"git notes merge --reset [-v | -q]",
 	"git notes [--ref <notes_ref>] remove [<object>]",
 	"git notes [--ref <notes_ref>] prune [-n | -v]",
 	NULL
@@ -65,6 +67,8 @@ static const char * const git_notes_show_usage[] = {
 
 static const char * const git_notes_merge_usage[] = {
 	"git notes merge [<options>] <notes_ref>",
+	"git notes merge --commit [<options>]",
+	"git notes merge --reset [<options>]",
 	NULL
 };
 
@@ -761,32 +765,119 @@ static int show(int argc, const char **argv, const char *prefix)
 	return retval;
 }
 
+static int merge_reset(struct notes_merge_options *o)
+{
+	int ret = 0;
+
+	/*
+	 * Remove .git/NOTES_MERGE_PARTIAL and .git/NOTES_MERGE_REF, and call
+	 * notes_merge_reset() to remove .git/NOTES_MERGE_WORKTREE.
+	 */
+
+	if (delete_ref("NOTES_MERGE_PARTIAL", NULL, 0))
+		ret += error("Failed to delete ref NOTES_MERGE_PARTIAL");
+	if (delete_ref("NOTES_MERGE_REF", NULL, REF_NODEREF))
+		ret += error("Failed to delete ref NOTES_MERGE_REF");
+	if (notes_merge_reset(o))
+		ret += error("Failed to remove 'git notes merge' worktree");
+	return ret;
+}
+
+static int merge_commit(struct notes_merge_options *o)
+{
+	struct strbuf msg = STRBUF_INIT;
+	unsigned char sha1[20];
+	struct notes_tree *t;
+	struct commit *partial;
+	struct pretty_print_context pretty_ctx;
+
+	/*
+	 * Read partial merge result from .git/NOTES_MERGE_PARTIAL,
+	 * and target notes ref from .git/NOTES_MERGE_REF.
+	 */
+
+	if (get_sha1("NOTES_MERGE_PARTIAL", sha1))
+		die("Failed to read ref NOTES_MERGE_PARTIAL");
+	else if (!(partial = lookup_commit_reference(sha1)))
+		die("Could not find commit from NOTES_MERGE_PARTIAL.");
+	else if (parse_commit(partial))
+		die("Could not parse commit from NOTES_MERGE_PARTIAL.");
+
+	t = xcalloc(1, sizeof(struct notes_tree));
+	init_notes(t, "NOTES_MERGE_PARTIAL", combine_notes_overwrite, 0);
+
+	o->local_ref = resolve_ref("NOTES_MERGE_REF", sha1, 0, 0);
+	if (!o->local_ref)
+		die("Failed to resolve NOTES_MERGE_REF");
+
+	if (notes_merge_commit(o, t, partial, sha1))
+		die("Failed to finalize notes merge");
+
+	/* Reuse existing commit message in reflog message */
+	memset(&pretty_ctx, 0, sizeof(pretty_ctx));
+	format_commit_message(partial, "%s", &msg, &pretty_ctx);
+	strbuf_trim(&msg);
+	strbuf_insert(&msg, 0, "notes: ", 7);
+	update_ref(msg.buf, o->local_ref, sha1, NULL, 0, DIE_ON_ERR);
+
+	free_notes(t);
+	strbuf_release(&msg);
+	return merge_reset(o);
+}
+
 static int merge(int argc, const char **argv, const char *prefix)
 {
 	struct strbuf remote_ref = STRBUF_INIT, msg = STRBUF_INIT;
 	unsigned char result_sha1[20];
 	struct notes_tree *t;
 	struct notes_merge_options o;
+	int do_merge = 0, do_commit = 0, do_reset = 0;
 	int verbosity = 0, result;
 	const char *strategy = NULL;
 	struct option options[] = {
+		OPT_GROUP("General options"),
 		OPT__VERBOSITY(&verbosity),
+		OPT_GROUP("Merge options"),
 		OPT_STRING('s', "strategy", &strategy, "strategy",
 			   "resolve notes conflicts using the given "
 			   "strategy (manual/ours/theirs/union)"),
+		OPT_GROUP("Committing unmerged notes"),
+		{ OPTION_BOOLEAN, 0, "commit", &do_commit, NULL,
+			"finalize notes merge by committing unmerged notes",
+			PARSE_OPT_NOARG | PARSE_OPT_NONEG },
+		OPT_GROUP("Aborting notes merge resolution"),
+		{ OPTION_BOOLEAN, 0, "reset", &do_reset, NULL,
+			"abort notes merge",
+			PARSE_OPT_NOARG | PARSE_OPT_NONEG },
 		OPT_END()
 	};
 
 	argc = parse_options(argc, argv, prefix, options,
 			     git_notes_merge_usage, 0);
 
-	if (argc != 1) {
+	if (strategy || do_commit + do_reset == 0)
+		do_merge = 1;
+	if (do_commit + do_reset + do_merge != 1) {
+		error("cannot mix --commit, --reset or -s/--strategy");
+		usage_with_options(git_notes_merge_usage, options);
+	}
+
+	if (do_merge && argc != 1) {
 		error("Must specify a notes ref to merge");
 		usage_with_options(git_notes_merge_usage, options);
+	} else if (!do_merge && argc) {
+		error("too many parameters");
+		usage_with_options(git_notes_merge_usage, options);
 	}
 
 	init_notes_merge_options(&o);
 	o.verbosity = verbosity + 2; // default verbosity level is 2
+
+	if (do_reset)
+		return merge_reset(&o);
+	if (do_commit)
+		return merge_commit(&o);
+
 	o.local_ref = default_notes_ref();
 	strbuf_addstr(&remote_ref, argv[0]);
 	expand_notes_ref(&remote_ref);
@@ -819,9 +910,19 @@ static int merge(int argc, const char **argv, const char *prefix)
 		/* Update default notes ref with new commit */
 		update_ref(msg.buf, default_notes_ref(), result_sha1, NULL,
 			   0, DIE_ON_ERR);
-	else /* Merge has unresolved conflicts */
-		printf("Automatic notes merge failed. Fix conflicts in %s.\n",
+	else { /* Merge has unresolved conflicts */
+		/* Update .git/NOTES_MERGE_PARTIAL with partial merge result */
+		update_ref(msg.buf, "NOTES_MERGE_PARTIAL", result_sha1, NULL,
+			   0, DIE_ON_ERR);
+		/* Store ref-to-be-updated into .git/NOTES_MERGE_REF */
+		if (create_symref("NOTES_MERGE_REF", default_notes_ref(), NULL))
+			die("Failed to store link to current notes ref (%s)",
+			    default_notes_ref());
+		printf("Automatic notes merge failed. Fix conflicts in %s and "
+		       "commit the result with 'git notes merge --commit', or "
+		       "abort the merge with 'git notes merge --reset'.\n",
 		       git_path(NOTES_MERGE_WORKTREE));
+	}
 
 	free_notes(t);
 	strbuf_release(&remote_ref);
diff --git a/notes-merge.c b/notes-merge.c
index 8efa003..cf1f8da 100644
--- a/notes-merge.c
+++ b/notes-merge.c
@@ -632,3 +632,72 @@ found_result:
 	       result, sha1_to_hex(result_sha1));
 	return result;
 }
+
+int notes_merge_commit(struct notes_merge_options *o,
+		       struct notes_tree *partial_tree,
+		       struct commit *partial_commit,
+		       unsigned char *result_sha1)
+{
+	/*
+	 * Iterate through files in .git/NOTES_MERGE_WORKTREE and add all
+	 * found notes to 'partial_tree'. Write the updates notes tree to
+	 * the DB, and commit the resulting tree object while reusing the
+	 * commit message and parents from 'partial_commit'.
+	 * Finally store the new commit object SHA1 into 'result_sha1'.
+	 */
+	struct dir_struct dir;
+	const char *path = git_path(NOTES_MERGE_WORKTREE "/");
+	int path_len = strlen(path), i;
+	const char *msg = strstr(partial_commit->buffer, "\n\n");
+
+	OUTPUT(o, 3, "Committing notes in notes merge worktree at %.*s",
+	       path_len - 1, path);
+
+	if (!msg || msg[2] == '\0')
+		die("partial notes commit has empty message");
+	msg += 2;
+
+	memset(&dir, 0, sizeof(dir));
+	read_directory(&dir, path, path_len, NULL);
+	for (i = 0; i < dir.nr; i++) {
+		struct dir_entry *ent = dir.entries[i];
+		struct stat st;
+		const char *relpath = ent->name + path_len;
+		unsigned char obj_sha1[20], blob_sha1[20];
+
+		if (ent->len - path_len != 40 || get_sha1_hex(relpath, obj_sha1)) {
+			OUTPUT(o, 3, "Skipping non-SHA1 entry '%s'", ent->name);
+			continue;
+		}
+
+		/* write file as blob, and add to partial_tree */
+		if (stat(ent->name, &st))
+			die_errno("Failed to stat '%s'", ent->name);
+		if (index_path(blob_sha1, ent->name, &st, 1))
+			die("Failed to write blob object from '%s'", ent->name);
+		if (add_note(partial_tree, obj_sha1, blob_sha1, NULL))
+			die("Failed to add resolved note '%s' to notes tree",
+			    ent->name);
+		OUTPUT(o, 4, "Added resolved note for object %s: %s",
+		       sha1_to_hex(obj_sha1), sha1_to_hex(blob_sha1));
+	}
+
+	create_notes_commit(partial_tree, partial_commit->parents, msg,
+			    result_sha1);
+	OUTPUT(o, 4, "Finalized notes merge commit: %s",
+	       sha1_to_hex(result_sha1));
+	return 0;
+}
+
+int notes_merge_reset(struct notes_merge_options *o)
+{
+	/* Remove .git/NOTES_MERGE_WORKTREE directory and all files within */
+	struct strbuf buf = STRBUF_INIT;
+	int ret;
+
+	strbuf_addstr(&buf, git_path(NOTES_MERGE_WORKTREE));
+	OUTPUT(o, 3, "Removing notes merge worktree at %s", buf.buf);
+	ret = remove_dir_recursively(&buf, 0);
+	strbuf_release(&buf);
+	return ret;
+}
diff --git a/notes-merge.h b/notes-merge.h
index e9a8ce6..e2f3459 100644
--- a/notes-merge.h
+++ b/notes-merge.h
@@ -65,4 +65,27 @@ int notes_merge(struct notes_merge_options *o,
 		struct notes_tree *local_tree,
 		unsigned char *result_sha1);
 
+/*
+ * Finalize conflict resolution from an earlier notes_merge()
+ *
+ * The given notes tree 'partial_tree' must be the notes_tree corresponding to
+ * the given 'partial_commit', the partial result commit created by a previous
+ * call to notes_merge().
+ *
+ * This function will add the (now resolved) notes in .git/NOTES_MERGE_WORKTREE
+ * to 'partial_tree', and create a final notes merge commit, the SHA1 of which
+ * will be stored in 'result_sha1'.
+ */
+int notes_merge_commit(struct notes_merge_options *o,
+		       struct notes_tree *partial_tree,
+		       struct commit *partial_commit,
+		       unsigned char *result_sha1);
+
+/*
+ * Abort conflict resolution from an earlier notes_merge()
+ *
+ * Removes the notes merge worktree in .git/NOTES_MERGE_WORKTREE.
+ */
+int notes_merge_reset(struct notes_merge_options *o);
+
 #endif
diff --git a/t/t3310-notes-merge-manual-resolve.sh b/t/t3310-notes-merge-manual-resolve.sh
index eadb6b7..1db0649 100755
--- a/t/t3310-notes-merge-manual-resolve.sh
+++ b/t/t3310-notes-merge-manual-resolve.sh
@@ -171,6 +171,7 @@ cp expect_notes_y expect_notes_m
 cp expect_log_y expect_log_m
 
 git rev-parse refs/notes/y > pre_merge_y
+git rev-parse refs/notes/z > pre_merge_z
 
 test_expect_success 'merge z into m (== y) with default ("manual") resolver => Conflicting 3-way merge' '
 	git update-ref refs/notes/m refs/notes/y &&
@@ -289,4 +290,179 @@ test_expect_success 'can do merge without conflicts even if previous merge is un
 	verify_notes y
 '
 
+cat <<EOF | sort >expect_notes_m
+021faa20e931fb48986ffc6282b4bb05553ac946 $commit_sha4
+5772f42408c0dd6f097a7ca2d24de0e78d1c46b1 $commit_sha3
+283b48219aee9a4105f6cab337e789065c82c2b9 $commit_sha2
+0a59e787e6d688aa6309e56e8c1b89431a0fc1c1 $commit_sha1
+EOF
+
+cat >expect_log_m <<EOF
+$commit_sha5 5th
+
+$commit_sha4 4th
+y and z notes on 4th commit
+
+$commit_sha3 3rd
+y notes on 3rd commit
+
+$commit_sha2 2nd
+z notes on 2nd commit
+
+$commit_sha1 1st
+y and z notes on 1st commit
+
+EOF
+
+test_expect_success 'finalize conflicting merge (z => m)' '
+	# Resolve conflicts and finalize merge
+	cat >.git/NOTES_MERGE_WORKTREE/$commit_sha1 <<EOF &&
+y and z notes on 1st commit
+EOF
+	cat >.git/NOTES_MERGE_WORKTREE/$commit_sha4 <<EOF &&
+y and z notes on 4th commit
+EOF
+	git notes merge --commit &&
+	# No .git/NOTES_MERGE_* files left
+	test_must_fail ls .git/NOTES_MERGE_* >output 2>/dev/null &&
+	test_cmp /dev/null output &&
+	# Merge commit has pre-merge y and pre-merge z as parents
+	test "$(git rev-parse refs/notes/m^1)" = "$(cat pre_merge_y)" &&
+	test "$(git rev-parse refs/notes/m^2)" = "$(cat pre_merge_z)" &&
+	# Merge commit mentions the notes refs merged
+	git log -1 --format=%B refs/notes/m > merge_commit_msg &&
+	grep -q refs/notes/m merge_commit_msg &&
+	grep -q refs/notes/z merge_commit_msg &&
+	# Verify contents of merge result
+	verify_notes m &&
+	# Verify that other notes refs has not changed (w, x, y and z)
+	verify_notes w &&
+	verify_notes x &&
+	verify_notes y &&
+	verify_notes z
+'
+
+cat >expect_conflict_$commit_sha4 <<EOF
+<<<<<<< refs/notes/m
+y notes on 4th commit
+=======
+z notes on 4th commit
+
+More z notes on 4th commit
+>>>>>>> refs/notes/z
+EOF
+
+cp expect_notes_y expect_notes_m
+cp expect_log_y expect_log_m
+
+git rev-parse refs/notes/y > pre_merge_y
+git rev-parse refs/notes/z > pre_merge_z
+
+test_expect_success 'redo merge of z into m (== y) with default ("manual") resolver => Conflicting 3-way merge' '
+	git update-ref refs/notes/m refs/notes/y &&
+	git config core.notesRef refs/notes/m &&
+	test_must_fail git notes merge z >output &&
+	# Output should point to where to resolve conflicts
+	grep -q "\\.git/NOTES_MERGE_WORKTREE" output &&
+	# Inspect merge conflicts
+	ls .git/NOTES_MERGE_WORKTREE >output_conflicts &&
+	test_cmp expect_conflicts output_conflicts &&
+	( for f in $(cat expect_conflicts); do
+		test_cmp "expect_conflict_$f" ".git/NOTES_MERGE_WORKTREE/$f" ||
+		exit 1
+	done ) &&
+	# Verify that current notes tree (pre-merge) has not changed (m == y)
+	verify_notes y &&
+	verify_notes m &&
+	test "$(git rev-parse refs/notes/m)" = "$(cat pre_merge_y)"
+'
+
+test_expect_success 'abort notes merge' '
+	git notes merge --reset &&
+	# No .git/NOTES_MERGE_* files left
+	test_must_fail ls .git/NOTES_MERGE_* >output 2>/dev/null &&
+	test_cmp /dev/null output &&
+	# m has not moved (still == y)
+	test "$(git rev-parse refs/notes/m)" = "$(cat pre_merge_y)"
+	# Verify that other notes refs has not changed (w, x, y and z)
+	verify_notes w &&
+	verify_notes x &&
+	verify_notes y &&
+	verify_notes z
+'
+
+git rev-parse refs/notes/y > pre_merge_y
+git rev-parse refs/notes/z > pre_merge_z
+
+test_expect_success 'redo merge of z into m (== y) with default ("manual") resolver => Conflicting 3-way merge' '
+	test_must_fail git notes merge z >output &&
+	# Output should point to where to resolve conflicts
+	grep -q "\\.git/NOTES_MERGE_WORKTREE" output &&
+	# Inspect merge conflicts
+	ls .git/NOTES_MERGE_WORKTREE >output_conflicts &&
+	test_cmp expect_conflicts output_conflicts &&
+	( for f in $(cat expect_conflicts); do
+		test_cmp "expect_conflict_$f" ".git/NOTES_MERGE_WORKTREE/$f" ||
+		exit 1
+	done ) &&
+	# Verify that current notes tree (pre-merge) has not changed (m == y)
+	verify_notes y &&
+	verify_notes m &&
+	test "$(git rev-parse refs/notes/m)" = "$(cat pre_merge_y)"
+'
+
+cat <<EOF | sort >expect_notes_m
+304dfb4325cf243025b9957486eb605a9b51c199 $commit_sha5
+283b48219aee9a4105f6cab337e789065c82c2b9 $commit_sha2
+0a59e787e6d688aa6309e56e8c1b89431a0fc1c1 $commit_sha1
+EOF
+
+cat >expect_log_m <<EOF
+$commit_sha5 5th
+new note on 5th commit
+
+$commit_sha4 4th
+
+$commit_sha3 3rd
+
+$commit_sha2 2nd
+z notes on 2nd commit
+
+$commit_sha1 1st
+y and z notes on 1st commit
+
+EOF
+
+test_expect_success 'add + remove notes in finalized merge (z => m)' '
+	# Resolve one conflict
+	cat >.git/NOTES_MERGE_WORKTREE/$commit_sha1 <<EOF &&
+y and z notes on 1st commit
+EOF
+	# Remove another conflict
+	rm .git/NOTES_MERGE_WORKTREE/$commit_sha4 &&
+	# Remove a D/F conflict
+	rm .git/NOTES_MERGE_WORKTREE/$commit_sha3 &&
+	# Add a new note
+	echo "new note on 5th commit" > .git/NOTES_MERGE_WORKTREE/$commit_sha5 &&
+	# Finalize merge
+	git notes merge --commit &&
+	# No .git/NOTES_MERGE_* files left
+	test_must_fail ls .git/NOTES_MERGE_* >output 2>/dev/null &&
+	test_cmp /dev/null output &&
+	# Merge commit has pre-merge y and pre-merge z as parents
+	test "$(git rev-parse refs/notes/m^1)" = "$(cat pre_merge_y)" &&
+	test "$(git rev-parse refs/notes/m^2)" = "$(cat pre_merge_z)" &&
+	# Merge commit mentions the notes refs merged
+	git log -1 --format=%B refs/notes/m > merge_commit_msg &&
+	grep -q refs/notes/m merge_commit_msg &&
+	grep -q refs/notes/z merge_commit_msg &&
+	# Verify contents of merge result
+	verify_notes m &&
+	# Verify that other notes refs has not changed (w, x, y and z)
+	verify_notes w &&
+	verify_notes x &&
+	verify_notes y &&
+	verify_notes z
+'
+
 test_done
-- 
1.7.3.98.g5ad7d9

[PATCH 15/18] git notes merge: List conflicting notes in notes merge commit message

[Johan Herland]

This brings notes merge in line with regular merge's behaviour.

Signed-off-by: Johan Herland <johan@herland.net>
---
 builtin/notes.c                       |    2 +-
 notes-merge.c                         |   11 ++++++++++-
 notes-merge.h                         |    2 +-
 t/t3310-notes-merge-manual-resolve.sh |   12 ++++++++++++
 4 files changed, 24 insertions(+), 3 deletions(-)

diff --git a/builtin/notes.c b/builtin/notes.c
index 8be7d9e..961dcbf 100644
--- a/builtin/notes.c
+++ b/builtin/notes.c
@@ -902,7 +902,7 @@ static int merge(int argc, const char **argv, const char *prefix)
 
 	strbuf_addf(&msg, "notes: Merged notes from %s into %s",
 		    remote_ref.buf, default_notes_ref());
-	o.commit_msg = msg.buf + 7; // skip "notes: " prefix
+	strbuf_add(&(o.commit_msg), msg.buf + 7, msg.len - 7); // skip "notes: "
 
 	result = notes_merge(&o, t, result_sha1);
 
diff --git a/notes-merge.c b/notes-merge.c
index cf1f8da..8b34a32 100644
--- a/notes-merge.c
+++ b/notes-merge.c
@@ -7,6 +7,7 @@
 #include "dir.h"
 #include "notes.h"
 #include "notes-merge.h"
+#include "strbuf.h"
 
 struct notes_merge_pair {
 	unsigned char obj[20], base[20], local[20], remote[20];
@@ -15,6 +16,7 @@ struct notes_merge_pair {
 void init_notes_merge_options(struct notes_merge_options *o)
 {
 	memset(o, 0, sizeof(struct notes_merge_options));
+	strbuf_init(&(o->commit_msg), 0);
 	o->verbosity = 2;
 }
 
@@ -383,6 +385,12 @@ static int merge_one_change_manual(struct notes_merge_options *o,
 	       sha1_to_hex(p->obj), sha1_to_hex(p->base),
 	       sha1_to_hex(p->local), sha1_to_hex(p->remote));
 
+	/* add "Conflicts:" section to commit message first time through */
+	if (!o->has_worktree)
+		strbuf_addstr(&(o->commit_msg), "\n\nConflicts:\n");
+
+	strbuf_addf(&(o->commit_msg), "\t%s\n", sha1_to_hex(p->obj));
+
 	OUTPUT(o, 2, "Auto-merging notes for %s", sha1_to_hex(p->obj));
 	check_notes_merge_worktree(o);
 	if (is_null_sha1(p->local)) {
@@ -622,12 +630,13 @@ int notes_merge(struct notes_merge_options *o,
 		struct commit_list *parents = NULL;
 		commit_list_insert(remote, &parents); /* LIFO order */
 		commit_list_insert(local, &parents);
-		create_notes_commit(local_tree, parents, o->commit_msg,
+		create_notes_commit(local_tree, parents, o->commit_msg.buf,
 				    result_sha1);
 	}
 
 found_result:
 	free_commit_list(bases);
+	strbuf_release(&(o->commit_msg));
 	OUTPUT(o, 5, "notes_merge(): result = %i, result_sha1 = %.7s",
 	       result, sha1_to_hex(result_sha1));
 	return result;
diff --git a/notes-merge.h b/notes-merge.h
index e2f3459..a6ccb6a 100644
--- a/notes-merge.h
+++ b/notes-merge.h
@@ -6,7 +6,7 @@
 struct notes_merge_options {
 	const char *local_ref;
 	const char *remote_ref;
-	const char *commit_msg;
+	struct strbuf commit_msg;
 	int verbosity;
 	enum {
 		NOTES_MERGE_RESOLVE_MANUAL = 0,
diff --git a/t/t3310-notes-merge-manual-resolve.sh b/t/t3310-notes-merge-manual-resolve.sh
index 1db0649..8568307 100755
--- a/t/t3310-notes-merge-manual-resolve.sh
+++ b/t/t3310-notes-merge-manual-resolve.sh
@@ -333,6 +333,12 @@ EOF
 	git log -1 --format=%B refs/notes/m > merge_commit_msg &&
 	grep -q refs/notes/m merge_commit_msg &&
 	grep -q refs/notes/z merge_commit_msg &&
+	# Merge commit mentions conflicting notes
+	grep -q "Conflicts" merge_commit_msg &&
+	( for sha1 in $(cat expect_conflicts); do
+		grep -q "$sha1" merge_commit_msg ||
+		exit 1
+	done ) &&
 	# Verify contents of merge result
 	verify_notes m &&
 	# Verify that other notes refs has not changed (w, x, y and z)
@@ -456,6 +462,12 @@ EOF
 	git log -1 --format=%B refs/notes/m > merge_commit_msg &&
 	grep -q refs/notes/m merge_commit_msg &&
 	grep -q refs/notes/z merge_commit_msg &&
+	# Merge commit mentions conflicting notes
+	grep -q "Conflicts" merge_commit_msg &&
+	( for sha1 in $(cat expect_conflicts); do
+		grep -q "$sha1" merge_commit_msg ||
+		exit 1
+	done ) &&
 	# Verify contents of merge result
 	verify_notes m &&
 	# Verify that other notes refs has not changed (w, x, y and z)
-- 
1.7.3.98.g5ad7d9

[PATCH 16/18] git notes merge: --commit should fail if underlying notes ref has moved

[Johan Herland]

When manually resolving a notes merge, if the merging ref has moved since
the merge started, we should fail to complete the merge, and alert the user
to what's going on.

This situation may arise if you start a 'git notes merge' which results in
conflicts, and you then update the current notes ref (using for example
'git notes add/copy/amend/edit/remove/prune', 'git update-ref', etc.),
before you get around to resolving the notes conflicts and calling
'git notes merge --commit'.

We detect this situation by comparing the first parent of the partial merge
commit (which was created when the merge started) to the current value of the
merging notes ref (pointed to by the .git/NOTES_MERGE_REF symref).

If we don't fail in this situation, the notes merge commit would overwrite
the updated notes ref, thus losing the changes that happened in the meantime.

The patch includes a testcase verifying that we fail correctly in this
situation.

Signed-off-by: Johan Herland <johan@herland.net>
---
 builtin/notes.c                       |   11 ++++-
 t/t3310-notes-merge-manual-resolve.sh |   76 +++++++++++++++++++++++++++++++++
 2 files changed, 85 insertions(+), 2 deletions(-)

diff --git a/builtin/notes.c b/builtin/notes.c
index 961dcbf..27cab4b 100644
--- a/builtin/notes.c
+++ b/builtin/notes.c
@@ -786,7 +786,7 @@ static int merge_reset(struct notes_merge_options *o)
 static int merge_commit(struct notes_merge_options *o)
 {
 	struct strbuf msg = STRBUF_INIT;
-	unsigned char sha1[20];
+	unsigned char sha1[20], parent_sha1[20];
 	struct notes_tree *t;
 	struct commit *partial;
 	struct pretty_print_context pretty_ctx;
@@ -803,6 +803,11 @@ static int merge_commit(struct notes_merge_options *o)
 	else if (parse_commit(partial))
 		die("Could not parse commit from NOTES_MERGE_PARTIAL.");
 
+	if (partial->parents)
+		hashcpy(parent_sha1, partial->parents->item->object.sha1);
+	else
+		hashclr(parent_sha1);
+
 	t = xcalloc(1, sizeof(struct notes_tree));
 	init_notes(t, "NOTES_MERGE_PARTIAL", combine_notes_overwrite, 0);
 
@@ -818,7 +823,9 @@ static int merge_commit(struct notes_merge_options *o)
 	format_commit_message(partial, "%s", &msg, &pretty_ctx);
 	strbuf_trim(&msg);
 	strbuf_insert(&msg, 0, "notes: ", 7);
-	update_ref(msg.buf, o->local_ref, sha1, NULL, 0, DIE_ON_ERR);
+	update_ref(msg.buf, o->local_ref, sha1,
+		   is_null_sha1(parent_sha1) ? NULL : parent_sha1,
+		   0, DIE_ON_ERR);
 
 	free_notes(t);
 	strbuf_release(&msg);
diff --git a/t/t3310-notes-merge-manual-resolve.sh b/t/t3310-notes-merge-manual-resolve.sh
index 8568307..dfd4954 100755
--- a/t/t3310-notes-merge-manual-resolve.sh
+++ b/t/t3310-notes-merge-manual-resolve.sh
@@ -477,4 +477,80 @@ EOF
 	verify_notes z
 '
 
+cp expect_notes_y expect_notes_m
+cp expect_log_y expect_log_m
+
+test_expect_success 'redo merge of z into m (== y) with default ("manual") resolver => Conflicting 3-way merge' '
+	git update-ref refs/notes/m refs/notes/y &&
+	test_must_fail git notes merge z >output &&
+	# Output should point to where to resolve conflicts
+	grep -q "\\.git/NOTES_MERGE_WORKTREE" output &&
+	# Inspect merge conflicts
+	ls .git/NOTES_MERGE_WORKTREE >output_conflicts &&
+	test_cmp expect_conflicts output_conflicts &&
+	( for f in $(cat expect_conflicts); do
+		test_cmp "expect_conflict_$f" ".git/NOTES_MERGE_WORKTREE/$f" ||
+		exit 1
+	done ) &&
+	# Verify that current notes tree (pre-merge) has not changed (m == y)
+	verify_notes y &&
+	verify_notes m &&
+	test "$(git rev-parse refs/notes/m)" = "$(cat pre_merge_y)"
+'
+
+cp expect_notes_w expect_notes_m
+cp expect_log_w expect_log_m
+
+test_expect_success 'reset notes ref m to somewhere else (w)' '
+	git update-ref refs/notes/m refs/notes/w &&
+	verify_notes m &&
+	test "$(git rev-parse refs/notes/m)" = "$(git rev-parse refs/notes/w)"
+'
+
+test_expect_success 'fail to finalize conflicting merge if underlying ref has moved in the meantime (m != NOTES_MERGE_PARTIAL^1)' '
+	# Resolve conflicts
+	cat >.git/NOTES_MERGE_WORKTREE/$commit_sha1 <<EOF &&
+y and z notes on 1st commit
+EOF
+	cat >.git/NOTES_MERGE_WORKTREE/$commit_sha4 <<EOF &&
+y and z notes on 4th commit
+EOF
+	# Fail to finalize merge
+	test_must_fail git notes merge --commit >output 2>&1 &&
+	# .git/NOTES_MERGE_* must remain
+	test -f .git/NOTES_MERGE_PARTIAL &&
+	test -f .git/NOTES_MERGE_REF &&
+	test -f .git/NOTES_MERGE_WORKTREE/$commit_sha1 &&
+	test -f .git/NOTES_MERGE_WORKTREE/$commit_sha2 &&
+	test -f .git/NOTES_MERGE_WORKTREE/$commit_sha3 &&
+	test -f .git/NOTES_MERGE_WORKTREE/$commit_sha4 &&
+	# Refs are unchanged
+	test "$(git rev-parse refs/notes/m)" = "$(git rev-parse refs/notes/w)"
+	test "$(git rev-parse refs/notes/y)" = "$(git rev-parse NOTES_MERGE_PARTIAL^1)"
+	test "$(git rev-parse refs/notes/m)" != "$(git rev-parse NOTES_MERGE_PARTIAL^1)"
+	# Mention refs/notes/m, and its current and expected value in output
+	grep -q "refs/notes/m" output &&
+	grep -q "$(git rev-parse refs/notes/m)" output &&
+	grep -q "$(git rev-parse NOTES_MERGE_PARTIAL^1)" output &&
+	# Verify that other notes refs has not changed (w, x, y and z)
+	verify_notes w &&
+	verify_notes x &&
+	verify_notes y &&
+	verify_notes z
+'
+
+test_expect_success 'resolve situation by aborting the notes merge' '
+	git notes merge --reset &&
+	# No .git/NOTES_MERGE_* files left
+	test_must_fail ls .git/NOTES_MERGE_* >output 2>/dev/null &&
+	test_cmp /dev/null output &&
+	# m has not moved (still == w)
+	test "$(git rev-parse refs/notes/m)" = "$(git rev-parse refs/notes/w)"
+	# Verify that other notes refs has not changed (w, x, y and z)
+	verify_notes w &&
+	verify_notes x &&
+	verify_notes y &&
+	verify_notes z
+'
+
 test_done
-- 
1.7.3.98.g5ad7d9

[PATCH 17/18] git notes merge: Add another auto-resolving strategy: "cat_sort_uniq"

[Johan Herland]

This new strategy is similar to "concatenate", but in addition to
concatenating the two note candidates, this strategy sorts the resulting
lines, and removes duplicate lines from the result. This is equivalent to
applying the "cat | sort | uniq" shell pipeline to the two note candidates.

This strategy is useful if the notes follow a line-based format where one
wants to avoid duplicate lines in the merge result.

Note that if either of the note candidates contain duplicate lines _prior_
to the merge, these will also be removed by this merge strategy.

The patch also contains tests and documentation for the new strategy.

Signed-off-by: Johan Herland <johan@herland.net>
---
 Documentation/git-notes.txt         |   12 +++-
 builtin/notes.c                     |    8 ++-
 notes-merge.c                       |    6 ++
 notes-merge.h                       |    3 +-
 notes.c                             |   76 ++++++++++++++++++
 notes.h                             |    1 +
 t/t3309-notes-merge-auto-resolve.sh |  145 +++++++++++++++++++++++++++++++++++
 7 files changed, 247 insertions(+), 4 deletions(-)

diff --git a/Documentation/git-notes.txt b/Documentation/git-notes.txt
index ede7755..874b77a 100644
--- a/Documentation/git-notes.txt
+++ b/Documentation/git-notes.txt
@@ -155,7 +155,7 @@ OPTIONS
 --strategy=<strategy>::
 	When merging notes, resolve notes conflicts using the given
 	strategy. The following strategies are recognized: "manual"
-	(default), "ours", "theirs" and "union".
+	(default), "ours", "theirs", "union" and "cat_sort_uniq".
 	See the "NOTES MERGE STRATEGIES" section below for more
 	information on each notes merge strategy.
 
@@ -231,6 +231,16 @@ ref).
 "union" automatically resolves notes conflicts by concatenating the
 local and remote versions.
 
+"cat_sort_uniq" is similar to "union", but in addition to concatenating
+the local and remote versions, this strategy also sorts the resulting
+lines, and removes duplicate lines from the result. This is equivalent
+to applying the "cat | sort | uniq" shell pipeline to the local and
+remote versions. This strategy is useful if the notes follow a line-based
+format where one wants to avoid duplicated lines in the merge result.
+Note that if either the local or remote version contain duplicate lines
+prior to the merge, these will also be removed by this notes merge
+strategy.
+
 
 EXAMPLES
 --------
diff --git a/builtin/notes.c b/builtin/notes.c
index 27cab4b..ddd8d54 100644
--- a/builtin/notes.c
+++ b/builtin/notes.c
@@ -324,6 +324,8 @@ combine_notes_fn parse_combine_notes_fn(const char *v)
 		return combine_notes_ignore;
 	else if (!strcasecmp(v, "concatenate"))
 		return combine_notes_concatenate;
+	else if (!strcasecmp(v, "cat_sort_uniq"))
+		return combine_notes_cat_sort_uniq;
 	else
 		return NULL;
 }
@@ -846,8 +848,8 @@ static int merge(int argc, const char **argv, const char *prefix)
 		OPT__VERBOSITY(&verbosity),
 		OPT_GROUP("Merge options"),
 		OPT_STRING('s', "strategy", &strategy, "strategy",
-			   "resolve notes conflicts using the given "
-			   "strategy (manual/ours/theirs/union)"),
+			   "resolve notes conflicts using the given strategy "
+			   "(manual/ours/theirs/union/cat_sort_uniq)"),
 		OPT_GROUP("Committing unmerged notes"),
 		{ OPTION_BOOLEAN, 0, "commit", &do_commit, NULL,
 			"finalize notes merge by committing unmerged notes",
@@ -899,6 +901,8 @@ static int merge(int argc, const char **argv, const char *prefix)
 			o.strategy = NOTES_MERGE_RESOLVE_THEIRS;
 		else if (!strcmp(strategy, "union"))
 			o.strategy = NOTES_MERGE_RESOLVE_UNION;
+		else if (!strcmp(strategy, "cat_sort_uniq"))
+			o.strategy = NOTES_MERGE_RESOLVE_CAT_SORT_UNIQ;
 		else {
 			error("Unknown -X/--resolve strategy: %s", strategy);
 			usage_with_options(git_notes_merge_usage, options);
diff --git a/notes-merge.c b/notes-merge.c
index 8b34a32..3d5be04 100644
--- a/notes-merge.c
+++ b/notes-merge.c
@@ -451,6 +451,12 @@ static int merge_one_change(struct notes_merge_options *o,
 		if (add_note(t, p->obj, p->remote, combine_notes_concatenate))
 			die("confused: combine_notes_concatenate failed");
 		return 0;
+	case NOTES_MERGE_RESOLVE_CAT_SORT_UNIQ:
+		OUTPUT(o, 2, "Concatenating unique lines in local and remote "
+		       "notes for %s", sha1_to_hex(p->obj));
+		if (add_note(t, p->obj, p->remote, combine_notes_cat_sort_uniq))
+			die("confused: combine_notes_cat_sort_uniq failed");
+		return 0;
 	}
 	die("Unknown strategy (%i).", o->strategy);
 }
diff --git a/notes-merge.h b/notes-merge.h
index a6ccb6a..0690f40 100644
--- a/notes-merge.h
+++ b/notes-merge.h
@@ -12,7 +12,8 @@ struct notes_merge_options {
 		NOTES_MERGE_RESOLVE_MANUAL = 0,
 		NOTES_MERGE_RESOLVE_OURS,
 		NOTES_MERGE_RESOLVE_THEIRS,
-		NOTES_MERGE_RESOLVE_UNION
+		NOTES_MERGE_RESOLVE_UNION,
+		NOTES_MERGE_RESOLVE_CAT_SORT_UNIQ
 	} strategy;
 	unsigned has_worktree:1;
 };
diff --git a/notes.c b/notes.c
index 28afe2c..5f846d9 100644
--- a/notes.c
+++ b/notes.c
@@ -847,6 +847,82 @@ int combine_notes_ignore(unsigned char *cur_sha1,
 	return 0;
 }
 
+static int string_list_add_note_lines(struct string_list *sort_uniq_list,
+				      const unsigned char *sha1)
+{
+	char *data;
+	unsigned long len;
+	enum object_type t;
+	struct strbuf buf = STRBUF_INIT;
+	struct strbuf **lines = NULL;
+	int i, list_index;
+
+	if (is_null_sha1(sha1))
+		return 0;
+
+	/* read_sha1_file NUL-terminates */
+	data = read_sha1_file(sha1, &t, &len);
+	if (t != OBJ_BLOB || !data || !len) {
+		free(data);
+		return t != OBJ_BLOB || !data;
+	}
+
+	strbuf_attach(&buf, data, len, len + 1);
+	lines = strbuf_split(&buf, '\n');
+
+	for (i = 0; lines[i]; i++) {
+		if (lines[i]->buf[lines[i]->len - 1] == '\n')
+			strbuf_setlen(lines[i], lines[i]->len - 1);
+		if (!lines[i]->len)
+			continue; /* skip empty lines */
+		list_index = string_list_find_insert_index(sort_uniq_list,
+							   lines[i]->buf, 0);
+		if (list_index < 0)
+			continue; /* skip duplicate lines */
+		string_list_insert_at_index(sort_uniq_list, list_index,
+					    lines[i]->buf);
+	}
+
+	strbuf_list_free(lines);
+	strbuf_release(&buf);
+	return 0;
+}
+
+static int string_list_join_lines_helper(struct string_list_item *item,
+					 void *cb_data)
+{
+	struct strbuf *buf = cb_data;
+	strbuf_addstr(buf, item->string);
+	strbuf_addch(buf, '\n');
+	return 0;
+}
+
+int combine_notes_cat_sort_uniq(unsigned char *cur_sha1,
+		const unsigned char *new_sha1)
+{
+	struct string_list sort_uniq_list = { NULL, 0, 0, 1 };
+	struct strbuf buf = STRBUF_INIT;
+	int ret = 1;
+
+	/* read both note blob objects into unique_lines */
+	if (string_list_add_note_lines(&sort_uniq_list, cur_sha1))
+		goto out;
+	if (string_list_add_note_lines(&sort_uniq_list, new_sha1))
+		goto out;
+
+	/* create a new blob object from sort_uniq_list */
+	if (for_each_string_list(&sort_uniq_list,
+				 string_list_join_lines_helper, &buf))
+		goto out;
+
+	ret = write_sha1_file(buf.buf, buf.len, blob_type, cur_sha1);
+
+out:
+	strbuf_release(&buf);
+	string_list_clear(&sort_uniq_list, 0);
+	return ret;
+}
+
 static int string_list_add_one_ref(const char *path, const unsigned char *sha1,
 				   int flag, void *cb)
 {
diff --git a/notes.h b/notes.h
index b372575..93a7365 100644
--- a/notes.h
+++ b/notes.h
@@ -27,6 +27,7 @@ typedef int (*combine_notes_fn)(unsigned char *cur_sha1, const unsigned char *ne
 int combine_notes_concatenate(unsigned char *cur_sha1, const unsigned char *new_sha1);
 int combine_notes_overwrite(unsigned char *cur_sha1, const unsigned char *new_sha1);
 int combine_notes_ignore(unsigned char *cur_sha1, const unsigned char *new_sha1);
+int combine_notes_cat_sort_uniq(unsigned char *cur_sha1, const unsigned char *new_sha1);
 
 /*
  * Notes tree object
diff --git a/t/t3309-notes-merge-auto-resolve.sh b/t/t3309-notes-merge-auto-resolve.sh
index 1a1fc7e..461fd84 100755
--- a/t/t3309-notes-merge-auto-resolve.sh
+++ b/t/t3309-notes-merge-auto-resolve.sh
@@ -499,4 +499,149 @@ test_expect_success 'merge z into y with "union" strategy => Non-conflicting 3-w
 	verify_notes y union
 '
 
+test_expect_success 'reset to pre-merge state (y)' '
+	git update-ref refs/notes/y refs/notes/y^1 &&
+	# Verify pre-merge state
+	verify_notes y y
+'
+
+cat <<EOF | sort >expect_notes_union2
+d682107b8bf7a7aea1e537a8d5cb6a12b60135f1 $commit_sha15
+5de7ea7ad4f47e7ff91989fb82234634730f75df $commit_sha14
+3a631fdb6f41b05b55d8f4baf20728ba8f6fccbc $commit_sha13
+a66055fa82f7a03fe0c02a6aba3287a85abf7c62 $commit_sha12
+7e3c53503a3db8dd996cb62e37c66e070b44b54d $commit_sha11
+b8d03e173f67f6505a76f6e00cf93440200dd9be $commit_sha10
+851e1638784a884c7dd26c5d41f3340f6387413a $commit_sha8
+357b6ca14c7afd59b7f8b8aaaa6b8b723771135b $commit_sha5
+e2bfd06a37dd2031684a59a6e2b033e212239c78 $commit_sha4
+5772f42408c0dd6f097a7ca2d24de0e78d1c46b1 $commit_sha3
+283b48219aee9a4105f6cab337e789065c82c2b9 $commit_sha2
+EOF
+
+cat >expect_log_union2 <<EOF
+$commit_sha15 15th
+z notes on 15th commit
+
+y notes on 15th commit
+
+$commit_sha14 14th
+y notes on 14th commit
+
+$commit_sha13 13th
+y notes on 13th commit
+
+$commit_sha12 12th
+y notes on 12th commit
+
+$commit_sha11 11th
+z notes on 11th commit
+
+$commit_sha10 10th
+x notes on 10th commit
+
+$commit_sha9 9th
+
+$commit_sha8 8th
+z notes on 8th commit
+
+$commit_sha7 7th
+
+$commit_sha6 6th
+
+$commit_sha5 5th
+z notes on 5th commit
+
+y notes on 5th commit
+
+$commit_sha4 4th
+y notes on 4th commit
+
+$commit_sha3 3rd
+y notes on 3rd commit
+
+$commit_sha2 2nd
+z notes on 2nd commit
+
+$commit_sha1 1st
+
+EOF
+
+test_expect_success 'merge y into z with "union" strategy => Non-conflicting 3-way merge' '
+	git config core.notesRef refs/notes/z &&
+	git notes merge --strategy=union y &&
+	verify_notes z union2
+'
+
+test_expect_success 'reset to pre-merge state (z)' '
+	git update-ref refs/notes/z refs/notes/z^1 &&
+	# Verify pre-merge state
+	verify_notes z z
+'
+
+cat <<EOF | sort >expect_notes_cat_sort_uniq
+6be90240b5f54594203e25d9f2f64b7567175aee $commit_sha15
+5de7ea7ad4f47e7ff91989fb82234634730f75df $commit_sha14
+3a631fdb6f41b05b55d8f4baf20728ba8f6fccbc $commit_sha13
+a66055fa82f7a03fe0c02a6aba3287a85abf7c62 $commit_sha12
+7e3c53503a3db8dd996cb62e37c66e070b44b54d $commit_sha11
+b8d03e173f67f6505a76f6e00cf93440200dd9be $commit_sha10
+851e1638784a884c7dd26c5d41f3340f6387413a $commit_sha8
+660311d7f78dc53db12ac373a43fca7465381a7e $commit_sha5
+e2bfd06a37dd2031684a59a6e2b033e212239c78 $commit_sha4
+5772f42408c0dd6f097a7ca2d24de0e78d1c46b1 $commit_sha3
+283b48219aee9a4105f6cab337e789065c82c2b9 $commit_sha2
+EOF
+
+cat >expect_log_cat_sort_uniq <<EOF
+$commit_sha15 15th
+y notes on 15th commit
+z notes on 15th commit
+
+$commit_sha14 14th
+y notes on 14th commit
+
+$commit_sha13 13th
+y notes on 13th commit
+
+$commit_sha12 12th
+y notes on 12th commit
+
+$commit_sha11 11th
+z notes on 11th commit
+
+$commit_sha10 10th
+x notes on 10th commit
+
+$commit_sha9 9th
+
+$commit_sha8 8th
+z notes on 8th commit
+
+$commit_sha7 7th
+
+$commit_sha6 6th
+
+$commit_sha5 5th
+y notes on 5th commit
+z notes on 5th commit
+
+$commit_sha4 4th
+y notes on 4th commit
+
+$commit_sha3 3rd
+y notes on 3rd commit
+
+$commit_sha2 2nd
+z notes on 2nd commit
+
+$commit_sha1 1st
+
+EOF
+
+test_expect_success 'merge y into z with "cat_sort_uniq" strategy => Non-conflicting 3-way merge' '
+	git notes merge --strategy=cat_sort_uniq y &&
+	verify_notes z cat_sort_uniq
+'
+
 test_done
-- 
1.7.3.98.g5ad7d9

[PATCH 18/18] git notes merge: Add testcases for merging notes trees at different fanouts

[Johan Herland]

Notes trees may exist at different fanout levels internally. This
implementation detail should not be visible to the user, and it should
certainly not affect the merging of notes tree.

This patch adds testcases verifying the correctness of 'git notes merge'
when merging notes trees at different fanout levels.

Signed-off-by: Johan Herland <johan@herland.net>
---
 t/t3311-notes-merge-fanout.sh |  436 +++++++++++++++++++++++++++++++++++++++++
 1 files changed, 436 insertions(+), 0 deletions(-)
 create mode 100755 t/t3311-notes-merge-fanout.sh

diff --git a/t/t3311-notes-merge-fanout.sh b/t/t3311-notes-merge-fanout.sh
new file mode 100755
index 0000000..d1c7b69
--- /dev/null
+++ b/t/t3311-notes-merge-fanout.sh
@@ -0,0 +1,436 @@
+#!/bin/sh
+#
+# Copyright (c) 2010 Johan Herland
+#
+
+test_description='Test notes merging at various fanout levels'
+
+. ./test-lib.sh
+
+verify_notes () {
+	notes_ref="$1"
+	commit="$2"
+	if test -f "expect_notes_$notes_ref"
+	then
+		git -c core.notesRef="refs/notes/$notes_ref" notes |
+			sort >"output_notes_$notes_ref" &&
+		test_cmp "expect_notes_$notes_ref" "output_notes_$notes_ref" ||
+			return 1
+	fi &&
+	git -c core.notesRef="refs/notes/$notes_ref" log --format="%H %s%n%N" \
+		"$commit" >"output_log_$notes_ref" &&
+	test_cmp "expect_log_$notes_ref" "output_log_$notes_ref"
+}
+
+verify_fanout () {
+	notes_ref="$1"
+	# Expect entire notes tree to have a fanout == 1
+	git rev-parse --quiet --verify "refs/notes/$notes_ref" >/dev/null &&
+	git ls-tree -r --name-only "refs/notes/$notes_ref" |
+	while read path
+	do
+		case "$path" in
+		??/??????????????????????????????????????)
+			: true
+			;;
+		*)
+			echo "Invalid path \"$path\"" &&
+			return 1
+			;;
+		esac
+	done
+}
+
+verify_no_fanout () {
+	notes_ref="$1"
+	# Expect entire notes tree to have a fanout == 0
+	git rev-parse --quiet --verify "refs/notes/$notes_ref" >/dev/null &&
+	git ls-tree -r --name-only "refs/notes/$notes_ref" |
+	while read path
+	do
+		case "$path" in
+		????????????????????????????????????????)
+			: true
+			;;
+		*)
+			echo "Invalid path \"$path\"" &&
+			return 1
+			;;
+		esac
+	done
+}
+
+# Set up a notes merge scenario with different kinds of conflicts
+test_expect_success 'setup a few initial commits with notes (notes ref: x)' '
+	git config core.notesRef refs/notes/x &&
+	for i in 1 2 3 4 5
+	do
+		test_commit "commit$i" >/dev/null &&
+		git notes add -m "notes for commit$i" || return 1
+	done
+'
+
+commit_sha1=$(git rev-parse commit1^{commit})
+commit_sha2=$(git rev-parse commit2^{commit})
+commit_sha3=$(git rev-parse commit3^{commit})
+commit_sha4=$(git rev-parse commit4^{commit})
+commit_sha5=$(git rev-parse commit5^{commit})
+
+cat <<EOF | sort >expect_notes_x
+aed91155c7a72c2188e781fdf40e0f3761b299db $commit_sha5
+99fab268f9d7ee7b011e091a436c78def8eeee69 $commit_sha4
+953c20ae26c7aa0b428c20693fe38bc687f9d1a9 $commit_sha3
+6358796131b8916eaa2dde6902642942a1cb37e1 $commit_sha2
+b02d459c32f0e68f2fe0981033bb34f38776ba47 $commit_sha1
+EOF
+
+cat >expect_log_x <<EOF
+$commit_sha5 commit5
+notes for commit5
+
+$commit_sha4 commit4
+notes for commit4
+
+$commit_sha3 commit3
+notes for commit3
+
+$commit_sha2 commit2
+notes for commit2
+
+$commit_sha1 commit1
+notes for commit1
+
+EOF
+
+test_expect_success 'sanity check (x)' '
+	verify_notes x commit5 &&
+	verify_no_fanout x
+'
+
+num=300
+
+cp expect_log_x expect_log_y
+
+test_expect_success 'Add a few hundred commits w/notes to trigger fanout (x -> y)' '
+	git update-ref refs/notes/y refs/notes/x &&
+	git config core.notesRef refs/notes/y &&
+	i=5 &&
+	while test $i -lt $num
+	do
+		i=$(($i + 1)) &&
+		test_commit "commit$i" >/dev/null &&
+		git notes add -m "notes for commit$i" || return 1
+	done &&
+	test "$(git rev-parse refs/notes/y)" != "$(git rev-parse refs/notes/x)" &&
+	# Expected number of commits and notes
+	test "$(git rev-list HEAD | wc -l)" = "$num" &&
+	test "$(git notes list | wc -l)" = "$num" &&
+	# 5 first notes unchanged
+	verify_notes y commit5
+'
+
+test_expect_success 'notes tree has fanout (y)' 'verify_fanout y'
+
+test_expect_success 'No-op merge (already included) (x => y)' '
+	git update-ref refs/notes/m refs/notes/y &&
+	git config core.notesRef refs/notes/m &&
+	git notes merge x &&
+	test "$(git rev-parse refs/notes/m)" = "$(git rev-parse refs/notes/y)"
+'
+
+test_expect_success 'Fast-forward merge (y => x)' '
+	git update-ref refs/notes/m refs/notes/x &&
+	git notes merge y &&
+	test "$(git rev-parse refs/notes/m)" = "$(git rev-parse refs/notes/y)"
+'
+
+cat <<EOF | sort >expect_notes_z
+9f506ee70e20379d7f78204c77b334f43d77410d $commit_sha3
+23a47d6ea7d589895faf800752054818e1e7627b $commit_sha2
+b02d459c32f0e68f2fe0981033bb34f38776ba47 $commit_sha1
+EOF
+
+cat >expect_log_z <<EOF
+$commit_sha5 commit5
+
+$commit_sha4 commit4
+
+$commit_sha3 commit3
+notes for commit3
+
+appended notes for commit3
+
+$commit_sha2 commit2
+new notes for commit2
+
+$commit_sha1 commit1
+notes for commit1
+
+EOF
+
+test_expect_success 'change some of the initial 5 notes (x -> z)' '
+	git update-ref refs/notes/z refs/notes/x &&
+	git config core.notesRef refs/notes/z &&
+	git notes add -f -m "new notes for commit2" commit2 &&
+	git notes append -m "appended notes for commit3" commit3 &&
+	git notes remove commit4 &&
+	git notes remove commit5 &&
+	verify_notes z commit5
+'
+
+test_expect_success 'notes tree has no fanout (z)' 'verify_no_fanout z'
+
+cp expect_log_z expect_log_m
+
+test_expect_success 'successful merge without conflicts (y => z)' '
+	git update-ref refs/notes/m refs/notes/z &&
+	git config core.notesRef refs/notes/m &&
+	git notes merge y &&
+	verify_notes m commit5 &&
+	# x/y/z unchanged
+	verify_notes x commit5 &&
+	verify_notes y commit5 &&
+	verify_notes z commit5
+'
+
+test_expect_success 'notes tree still has fanout after merge (m)' 'verify_fanout m'
+
+cat >expect_log_w <<EOF
+$commit_sha5 commit5
+
+$commit_sha4 commit4
+other notes for commit4
+
+$commit_sha3 commit3
+other notes for commit3
+
+$commit_sha2 commit2
+notes for commit2
+
+$commit_sha1 commit1
+other notes for commit1
+
+EOF
+
+test_expect_success 'introduce conflicting changes (y -> w)' '
+	git update-ref refs/notes/w refs/notes/y &&
+	git config core.notesRef refs/notes/w &&
+	git notes add -f -m "other notes for commit1" commit1 &&
+	git notes add -f -m "other notes for commit3" commit3 &&
+	git notes add -f -m "other notes for commit4" commit4 &&
+	git notes remove commit5 &&
+	verify_notes w commit5
+'
+
+cat >expect_log_m <<EOF
+$commit_sha5 commit5
+
+$commit_sha4 commit4
+other notes for commit4
+
+$commit_sha3 commit3
+other notes for commit3
+
+$commit_sha2 commit2
+new notes for commit2
+
+$commit_sha1 commit1
+other notes for commit1
+
+EOF
+
+test_expect_success 'successful merge using "ours" strategy (z => w)' '
+	git update-ref refs/notes/m refs/notes/w &&
+	git config core.notesRef refs/notes/m &&
+	git notes merge -s ours z &&
+	verify_notes m commit5 &&
+	# w/x/y/z unchanged
+	verify_notes w commit5 &&
+	verify_notes x commit5 &&
+	verify_notes y commit5 &&
+	verify_notes z commit5
+'
+
+test_expect_success 'notes tree still has fanout after merge (m)' 'verify_fanout m'
+
+cat >expect_log_m <<EOF
+$commit_sha5 commit5
+
+$commit_sha4 commit4
+
+$commit_sha3 commit3
+notes for commit3
+
+appended notes for commit3
+
+$commit_sha2 commit2
+new notes for commit2
+
+$commit_sha1 commit1
+other notes for commit1
+
+EOF
+
+test_expect_success 'successful merge using "theirs" strategy (z => w)' '
+	git update-ref refs/notes/m refs/notes/w &&
+	git notes merge -s theirs z &&
+	verify_notes m commit5 &&
+	# w/x/y/z unchanged
+	verify_notes w commit5 &&
+	verify_notes x commit5 &&
+	verify_notes y commit5 &&
+	verify_notes z commit5
+'
+
+test_expect_success 'notes tree still has fanout after merge (m)' 'verify_fanout m'
+
+cat >expect_log_m <<EOF
+$commit_sha5 commit5
+
+$commit_sha4 commit4
+other notes for commit4
+
+$commit_sha3 commit3
+other notes for commit3
+
+notes for commit3
+
+appended notes for commit3
+
+$commit_sha2 commit2
+new notes for commit2
+
+$commit_sha1 commit1
+other notes for commit1
+
+EOF
+
+test_expect_success 'successful merge using "union" strategy (z => w)' '
+	git update-ref refs/notes/m refs/notes/w &&
+	git notes merge -s union z &&
+	verify_notes m commit5 &&
+	# w/x/y/z unchanged
+	verify_notes w commit5 &&
+	verify_notes x commit5 &&
+	verify_notes y commit5 &&
+	verify_notes z commit5
+'
+
+test_expect_success 'notes tree still has fanout after merge (m)' 'verify_fanout m'
+
+cat >expect_log_m <<EOF
+$commit_sha5 commit5
+
+$commit_sha4 commit4
+other notes for commit4
+
+$commit_sha3 commit3
+appended notes for commit3
+notes for commit3
+other notes for commit3
+
+$commit_sha2 commit2
+new notes for commit2
+
+$commit_sha1 commit1
+other notes for commit1
+
+EOF
+
+test_expect_success 'successful merge using "cat_sort_uniq" strategy (z => w)' '
+	git update-ref refs/notes/m refs/notes/w &&
+	git notes merge -s cat_sort_uniq z &&
+	verify_notes m commit5 &&
+	# w/x/y/z unchanged
+	verify_notes w commit5 &&
+	verify_notes x commit5 &&
+	verify_notes y commit5 &&
+	verify_notes z commit5
+'
+
+test_expect_success 'notes tree still has fanout after merge (m)' 'verify_fanout m'
+
+# We're merging z into w. Here are the conflicts we expect:
+#
+# commit | x -> w    | x -> z    | conflict?
+# -------|-----------|-----------|----------
+# 1      | changed   | unchanged | no, use w
+# 2      | unchanged | changed   | no, use z
+# 3      | changed   | changed   | yes (w, then z in conflict markers)
+# 4      | changed   | deleted   | yes (w)
+# 5      | deleted   | deleted   | no, deleted
+
+test_expect_success 'fails to merge using "manual" strategy (z => w)' '
+	git update-ref refs/notes/m refs/notes/w &&
+	test_must_fail git notes merge z
+'
+
+test_expect_success 'notes tree still has fanout after merge (m)' 'verify_fanout m'
+
+cat <<EOF | sort >expect_conflicts
+$commit_sha3
+$commit_sha4
+EOF
+
+cat >expect_conflict_$commit_sha3 <<EOF
+<<<<<<< refs/notes/m
+other notes for commit3
+=======
+notes for commit3
+
+appended notes for commit3
+>>>>>>> refs/notes/z
+EOF
+
+cat >expect_conflict_$commit_sha4 <<EOF
+other notes for commit4
+EOF
+
+test_expect_success 'verify conflict entries (with no fanout)' '
+	ls .git/NOTES_MERGE_WORKTREE >output_conflicts &&
+	test_cmp expect_conflicts output_conflicts &&
+	( for f in $(cat expect_conflicts); do
+		test_cmp "expect_conflict_$f" ".git/NOTES_MERGE_WORKTREE/$f" ||
+		exit 1
+	done ) &&
+	# Verify that current notes tree (pre-merge) has not changed (m == w)
+	test "$(git rev-parse refs/notes/m)" = "$(git rev-parse refs/notes/w)"
+'
+
+cat >expect_log_m <<EOF
+$commit_sha5 commit5
+
+$commit_sha4 commit4
+other notes for commit4
+
+$commit_sha3 commit3
+other notes for commit3
+
+appended notes for commit3
+
+$commit_sha2 commit2
+new notes for commit2
+
+$commit_sha1 commit1
+other notes for commit1
+
+EOF
+
+test_expect_success 'resolve and finalize merge (z => w)' '
+	cat >.git/NOTES_MERGE_WORKTREE/$commit_sha3 <<EOF &&
+other notes for commit3
+
+appended notes for commit3
+EOF
+	git notes merge --commit &&
+	verify_notes m commit5 &&
+	# w/x/y/z unchanged
+	verify_notes w commit5 &&
+	verify_notes x commit5 &&
+	verify_notes y commit5 &&
+	verify_notes z commit5
+'
+
+test_expect_success 'notes tree still has fanout after merge (m)' 'verify_fanout m'
+
+test_done
-- 
1.7.3.98.g5ad7d9

Re: [PATCH 00/18] git notes merge

[Sverre Rabbelier]

Heya,

On Wed, Sep 29, 2010 at 02:23, Johan Herland <johan@herland.net> wrote:
>  Alternatively, the user can call 'git notes merge --reset' to abort
>  the notes merge.

I'm torn, but I think that since we actually can here, we should call
it 'git notes merge --abort'. I know that there's no 'git merge
--abort', but IIRC that's for technical reasons only.

-- 
Cheers,

Sverre Rabbelier

Re: [PATCH 00/18] git notes merge

[Johan Herland]

On Wednesday 29 September 2010, Sverre Rabbelier wrote:
> On Wed, Sep 29, 2010 at 02:23, Johan Herland wrote:
> >  Alternatively, the user can call 'git notes merge --reset' to
> > abort the notes merge.
>
> I'm torn, but I think that since we actually can here, we should call
> it 'git notes merge --abort'.

Yeah, I'm torn as well. What about providing both? Or is that bloat?

> I know that there's no 'git merge --abort', but IIRC that's for
> technical reasons only. 

Maybe there _should_ be a 'git merge --abort' (as a synonym to 'git 
reset --merge')?


...Johan

-- 
Johan Herland, <johan@herland.net>
www.herland.net

Re: [PATCH 00/18] git notes merge

[Sverre Rabbelier]

Heya,

On Wed, Sep 29, 2010 at 17:16, Johan Herland <johan@herland.net> wrote:
> Yeah, I'm torn as well. What about providing both? Or is that bloat?

Definitely not both, that would be confusing, and would limit us if we
decide to add 'git merge --abort' later on.

>> I know that there's no 'git merge --abort', but IIRC that's for
>> technical reasons only.
>
> Maybe there _should_ be a 'git merge --abort' (as a synonym to 'git
> reset --merge')?

Hmmm, I don't know if that does what the user wants, (I haven't used
'git reset --merge' before), but if it does, that sounds like a good
solution.

-- 
Cheers,

Sverre Rabbelier

Re: [PATCH 00/18] git notes merge

[Johan Herland]

On Wednesday 29 September 2010, Sverre Rabbelier wrote:
> On Wed, Sep 29, 2010 at 17:16, Johan Herland wrote:
> > Yeah, I'm torn as well. What about providing both? Or is that
> > bloat?
>
> Definitely not both, that would be confusing, and would limit us if
> we decide to add 'git merge --abort' later on.

Yeah, but for consistency's sake I don't want to name it 'git notes 
merge --abort' if there's not a corresponding 'git merge --abort'.

> >> I know that there's no 'git merge --abort', but IIRC that's for
> >> technical reasons only.
> >
> > Maybe there _should_ be a 'git merge --abort' (as a synonym to 'git
> > reset --merge')?
>
> Hmmm, I don't know if that does what the user wants, (I haven't used
> 'git reset --merge' before), but if it does, that sounds like a good
> solution.

>From git-merge(1):

"If you tried a merge which resulted in complex conflicts and want to 
start over, you can recover with git reset --merge."

AFAICS, there's no better candidate synonym for 'git merge --abort'.


...Johan

-- 
Johan Herland, <johan@herland.net>
www.herland.net

Re: [PATCH 14/18] git notes merge: Manual conflict resolution, part 2/2

[Ævar Arnfjörð Bjarmason]

On Wed, Sep 29, 2010 at 00:23, Johan Herland <johan@herland.net> wrote:

> +--commit::
> +       Finalize an in-progress 'git notes merge', i.e. a notes merge with
> +       conflicts. When 'git notes merge' encounters conflicts, it s
> +       which returned one or more conflicts (that you have now resolved)

This "it s ..." sentence doesn't make sense.

Re: [PATCH 10/18] git notes merge: Handle real, non-conflicting notes merges

[Ævar Arnfjörð Bjarmason]

On Wed, Sep 29, 2010 at 00:23, Johan Herland <johan@herland.net> wrote:

> +       o.commit_msg = msg.buf + 7; // skip "notes: " prefix

Don't use C99 comments.

Re: [PATCH 10/18] git notes merge: Handle real, non-conflicting notes merges

[Johan Herland]

On Wednesday 29 September 2010, Ævar Arnfjörð Bjarmason wrote:
> On Wed, Sep 29, 2010 at 00:23, Johan Herland <johan@herland.net> wrote:
> > +       o.commit_msg = msg.buf + 7; // skip "notes: " prefix
> 
> Don't use C99 comments.

Thanks. Fix will be in the next iteration.

...Johan

-- 
Johan Herland, <johan@herland.net>
www.herland.net

Re: [PATCH 14/18] git notes merge: Manual conflict resolution, part 2/2

[Johan Herland]

On Wednesday 29 September 2010, Ævar Arnfjörð Bjarmason wrote:
> On Wed, Sep 29, 2010 at 00:23, Johan Herland <johan@herland.net> wrote:
> > +--commit::
> > +       Finalize an in-progress 'git notes merge', i.e. a notes merge
> > with +       conflicts. When 'git notes merge' encounters conflicts,
> > it s +       which returned one or more conflicts (that you have now
> > resolved)
> 
> This "it s ..." sentence doesn't make sense.

Indeed. Will be fixed in the next iteration. Here's the updated text:

--commit::
	Finalize an in-progress 'git notes merge'. Use this option
	when you have resolved the conflicts that 'git notes merge'
	stored in .git/NOTES_MERGE_WORKTREE. This amends the partial
	merge commit created by 'git notes merge' (stored in
	.git/NOTES_MERGE_PARTIAL) by adding the notes in
	.git/NOTES_MERGE_WORKTREE. The notes ref stored in the
	.git/NOTES_MERGE_REF symref is updated to the resulting commit.


...Johan

-- 
Johan Herland, <johan@herland.net>
www.herland.net

Re: [PATCH 12/18] Documentation: Preliminary docs on 'git notes merge'

[Stephen Boyd]

On 09/28/2010 05:23 PM, Johan Herland wrote:
> ++
> +If conflicts arise (and a strategy for automatically resolving
> +conflicting notes (see the -s/--strategy option) is not given,
> +the merge fails (TODO).

Unbalanced '(' here. Can you just drop the first one?

Re: [PATCH 11/18] git notes merge: Add automatic conflict resolvers (ours, theirs, union)

[Stephen Boyd]

On 09/28/2010 05:23 PM, Johan Herland wrote:
> @@ -788,6 +792,21 @@ static int merge(int argc, const char **argv, const char *prefix)
>  	expand_notes_ref(&remote_ref);
>  	o.remote_ref = remote_ref.buf;
>  
> +	if (strategy) {
> +		if (!strcmp(strategy, "manual"))
> +			o.strategy = NOTES_MERGE_RESOLVE_MANUAL;
> +		else if (!strcmp(strategy, "ours"))
> +			o.strategy = NOTES_MERGE_RESOLVE_OURS;
> +		else if (!strcmp(strategy, "theirs"))
> +			o.strategy = NOTES_MERGE_RESOLVE_THEIRS;
> +		else if (!strcmp(strategy, "union"))
> +			o.strategy = NOTES_MERGE_RESOLVE_UNION;
> +		else {
> +			error("Unknown -X/--resolve strategy: %s", strategy);

Is it -X/--resolve or -s/--strategy? This error confuses me.

> diff --git a/notes-merge.c b/notes-merge.c
> index f625ebd..6fa59d8 100644
> --- a/notes-merge.c
> +++ b/notes-merge.c
> @@ -262,6 +262,35 @@ static void diff_tree_local(struct notes_merge_options *o,
>  	diff_tree_release_paths(&opt);
>  }
>  
> +static int merge_one_change(struct notes_merge_options *o,
> +			    struct notes_merge_pair *p, struct notes_tree *t)
> +{
> +	/*
> +	 * Return 0 if change was resolved (and added to notes_tree),
> +	 * 1 if conflict
> +	 */
> +	switch (o->strategy) {
> +	case NOTES_MERGE_RESOLVE_MANUAL:
> +		return 1;
> +	case NOTES_MERGE_RESOLVE_OURS:
> +		OUTPUT(o, 2, "Using local notes for %s", sha1_to_hex(p->obj));
> +		/* nothing to do */
> +		return 0;
> +	case NOTES_MERGE_RESOLVE_THEIRS:
> +		OUTPUT(o, 2, "Using remote notes for %s", sha1_to_hex(p->obj));
> +		if (add_note(t, p->obj, p->remote, combine_notes_overwrite))
> +			die("confused: combine_notes_overwrite failed");

This will say:

fatal: confused: combine_notes_overwrite failed

Do we actually need the "confused" part? Heh, maybe we need a confused()
function?

Re: [PATCH 11/18] git notes merge: Add automatic conflict resolvers (ours, theirs, union)

[Johan Herland]

On Saturday 2. October 2010 11.14.46 Stephen Boyd wrote:
> On 09/28/2010 05:23 PM, Johan Herland wrote:
> > @@ -788,6 +792,21 @@ static int merge(int argc, const char **argv, const
> > char *prefix)
> > 
> >  	expand_notes_ref(&remote_ref);
> >  	o.remote_ref = remote_ref.buf;
> > 
> > +	if (strategy) {
> > +		if (!strcmp(strategy, "manual"))
> > +			o.strategy = NOTES_MERGE_RESOLVE_MANUAL;
> > +		else if (!strcmp(strategy, "ours"))
> > +			o.strategy = NOTES_MERGE_RESOLVE_OURS;
> > +		else if (!strcmp(strategy, "theirs"))
> > +			o.strategy = NOTES_MERGE_RESOLVE_THEIRS;
> > +		else if (!strcmp(strategy, "union"))
> > +			o.strategy = NOTES_MERGE_RESOLVE_UNION;
> > +		else {
> > +			error("Unknown -X/--resolve strategy: %s", strategy);
> 
> Is it -X/--resolve or -s/--strategy? This error confuses me.

No, the message should say "Unknown -s/--strategy: %s". Will be fixed in the 
next iteration. Thanks for noticing.

> > diff --git a/notes-merge.c b/notes-merge.c
> > index f625ebd..6fa59d8 100644
> > --- a/notes-merge.c
> > +++ b/notes-merge.c
> > @@ -262,6 +262,35 @@ static void diff_tree_local(struct
> > notes_merge_options *o,
> > 
> >  	diff_tree_release_paths(&opt);
> >  
> >  }
> > 
> > +static int merge_one_change(struct notes_merge_options *o,
> > +			    struct notes_merge_pair *p, struct notes_tree *t)
> > +{
> > +	/*
> > +	 * Return 0 if change was resolved (and added to notes_tree),
> > +	 * 1 if conflict
> > +	 */
> > +	switch (o->strategy) {
> > +	case NOTES_MERGE_RESOLVE_MANUAL:
> > +		return 1;
> > +	case NOTES_MERGE_RESOLVE_OURS:
> > +		OUTPUT(o, 2, "Using local notes for %s", sha1_to_hex(p->obj));
> > +		/* nothing to do */
> > +		return 0;
> > +	case NOTES_MERGE_RESOLVE_THEIRS:
> > +		OUTPUT(o, 2, "Using remote notes for %s", sha1_to_hex(p-
>obj));
> > +		if (add_note(t, p->obj, p->remote, combine_notes_overwrite))
> > +			die("confused: combine_notes_overwrite failed");
> 
> This will say:
> 
> fatal: confused: combine_notes_overwrite failed
> 
> Do we actually need the "confused" part? Heh, maybe we need a confused()
> function?

Well, combine_notes_overwrite() can only return 0, so if we get a non-zero 
return here I will certainly be confused, since this should be impossible. 
Maybe better to drop the check altogether and simply leave add_note(...)?


Have fun! :)

...Johan

-- 
Johan Herland, <johan@herland.net>
www.herland.net

Re: [PATCH 12/18] Documentation: Preliminary docs on 'git notes merge'

[Johan Herland]

On Saturday 2. October 2010 10.55.33 Stephen Boyd wrote:
> On 09/28/2010 05:23 PM, Johan Herland wrote:
> > ++
> > +If conflicts arise (and a strategy for automatically resolving
> > +conflicting notes (see the -s/--strategy option) is not given,
> > +the merge fails (TODO).
> 
> Unbalanced '(' here. Can you just drop the first one?

Done. Will be in next iteration.


Thanks,

...Johan

-- 
Johan Herland, <johan@herland.net>
www.herland.net

Re: [PATCH 01/18] (trivial) notes.h: Minor documentation fixes to copy_notes()

[Jonathan Nieder]

Johan Herland wrote:

> --- a/notes.h
> +++ b/notes.h
> @@ -104,6 +104,10 @@ const unsigned char *get_note(struct notes_tree *t,
>   * Copy a note from one object to another in the given notes_tree.
>   *
>   * Fails if the to_obj already has a note unless 'force' is true.
> + *
> + * IMPORTANT: The changes made by copy_note() to the given notes_tree structure
> + * are not persistent until a subsequent call to write_notes_tree() returns
> + * zero.

This reminds me: I sometimes wish there were a
Documentation/technical/api-notes.txt giving a high-level overview of
the API, something like this to start (warning: formatting probably
broken):

-- 8< --
notes API
=========

So you want to write or access persistent, per-object text?  The notes
API might help.

Calling sequence
----------------

The caller:

* Allocates and clears a `struct notes_tree`, then fills it based on a
  new or existing notes ref with `init_notes()`.

* Adds, removes, and retrieves notes as desired:

  . To add notes: use `write_sha1_file()` to create a blob object
    containing the information to be stored, and add it to the
    in-core notes tree with `add_note()`.

  . Retrieve notes as blob objects with `get_note()`, or as
    text with `format_note()`.

  . Change which objects a note is attached to with `copy_note()`
    and `remove_note()`.

* Can iterate over all notes with `for_each_note()`.

* Can remove notes attached to missing objects with `prune_notes()`.

* (Optionally) makes changes persist with `write_notes_tree()`.

* Frees resources associated to the notes tree with `free_notes()`.

A program like 'git log' that needs to find the notes corresponding
to certain objects in multiple notes trees might instead use the
display notes API.  In this case, the caller:

* (Optionally) prepares a `struct display_notes_opt` with settings
  about which notes trees to use.

* Initializes the display notes machinery with `init_display_notes()`.

* Retrieves notes for each object of interest with
  `format_display_notes()`.
-- >8 --

Re: [PATCH 03/18] notes.h/c: Clarify the handling of notes objects that are == null_sha1

[Jonathan Nieder]

Johan Herland wrote:

> The only functional changes in this patch concern the handling of null_sha1
> in notes_tree_insert(). Otherwise the patch consists solely of reordering
> functions in notes.c to avoid use-before-declaration

Would it makes sense to split off that no-op as a separate patch?

> --- a/notes.c
> +++ b/notes.c
> @@ -175,7 +248,10 @@ static void note_tree_insert(struct notes_tree *t, struct int_node *tree,
>  	switch (GET_PTR_TYPE(*p)) {
>  	case PTR_TYPE_NULL:
>  		assert(!*p);
> -		*p = SET_PTR_TYPE(entry, type);
> +		if (is_null_sha1(entry->val_sha1))
> +			free(entry);
> +		else
> +			*p = SET_PTR_TYPE(entry, type);
>  		return;
>  	case PTR_TYPE_NOTE:
>  		switch (type) {

No note present, but the node for one is.  This skips insertion of
empty notes, for consistency with:

> @@ -191,6 +267,9 @@ static void note_tree_insert(struct notes_tree *t, struct int_node *tree,
>  					    sha1_to_hex(l->val_sha1),
>  					    sha1_to_hex(entry->val_sha1),
>  					    sha1_to_hex(l->key_sha1));
> +
> +				if (is_null_sha1(l->val_sha1))
> +					note_tree_remove(t, tree, n, entry);

The note-present case, where the combine_notes() function can
return a null sha1 to request that a note be removed.

>  				free(entry);
>  				return;
>  			}
> @@ -222,6 +301,10 @@ static void note_tree_insert(struct notes_tree *t, struct int_node *tree,
>  	/* non-matching leaf_node */
>  	assert(GET_PTR_TYPE(*p) == PTR_TYPE_NOTE ||
>  	       GET_PTR_TYPE(*p) == PTR_TYPE_SUBTREE);
> +	if (is_null_sha1(entry->val_sha1)) { /* skip insertion of empty note */
> +		free(entry);
> +		return;
> +	}

The more usual no-note-present case.  Again, this skips insertion
of empty notes.

Do I understand correctly that the point of the main point of
this patch is to allow combine_notes() functions to request
that a note be deleted?  If so, it would be nice if the commit
message said so.

Regardless, for what it's worth,
Acked-by: Jonathan Nieder <jrnieder@gmail.com>

Re: [PATCH 01/18] (trivial) notes.h: Minor documentation fixes to copy_notes()

[Johan Herland]

On Tuesday 5. October 2010 16.55.43 Jonathan Nieder wrote:
> Johan Herland wrote:
> > --- a/notes.h
> > +++ b/notes.h
> > @@ -104,6 +104,10 @@ const unsigned char *get_note(struct notes_tree *t,
> > 
> >   * Copy a note from one object to another in the given notes_tree.
> >   *
> >   * Fails if the to_obj already has a note unless 'force' is true.
> > 
> > + *
> > + * IMPORTANT: The changes made by copy_note() to the given notes_tree structure
> > + * are not persistent until a subsequent call to write_notes_tree() returns
> > + * zero.
> 
> This reminds me: I sometimes wish there were a
> Documentation/technical/api-notes.txt giving a high-level overview of
> the API,

I thought studying the notes.h file and its comments was a sufficient
introduction on how to work with notes in code. I'm certainly biased,
though (as I obviously already know how to work with notes in code)...

If you believe that api-notes.txt is a valuable addition to
Documentation/, I have no problem ack-ing a patch that adds it.

> something like this to start (warning: formatting probably broken):
> 
> -- 8< --
> notes API
> =========
> 
> So you want to write or access persistent, per-object text?  The notes
> API might help.
> 
> Calling sequence
> ----------------
> 
> The caller:
> 
> * Allocates and clears a `struct notes_tree`, then fills it based on a
>   new or existing notes ref with `init_notes()`.
> 
> * Adds, removes, and retrieves notes as desired:
> 
>   . To add notes: use `write_sha1_file()` to create a blob object
>     containing the information to be stored, and add it to the
>     in-core notes tree with `add_note()`.
> 
>   . Retrieve notes as blob objects with `get_note()`, or as
>     text with `format_note()`.
> 
>   . Change which objects a note is attached to with `copy_note()`
>     and `remove_note()`.
> 
> * Can iterate over all notes with `for_each_note()`.
> 
> * Can remove notes attached to missing objects with `prune_notes()`.
> 
> * (Optionally) makes changes persist with `write_notes_tree()`.
> 
> * Frees resources associated to the notes tree with `free_notes()`.
> 
> A program like 'git log' that needs to find the notes corresponding
> to certain objects in multiple notes trees might instead use the
> display notes API.  In this case, the caller:
> 
> * (Optionally) prepares a `struct display_notes_opt` with settings
>   about which notes trees to use.
> 
> * Initializes the display notes machinery with `init_display_notes()`.
> 
> * Retrieves notes for each object of interest with
>   `format_display_notes()`.
> -- >8 --

This looks like a good start.


...Johan


-- 
Johan Herland, <johan@herland.net>
www.herland.net

Re: [PATCH 01/18] (trivial) notes.h: Minor documentation fixes to copy_notes()

[Jonathan Nieder]

Johan Herland wrote:

> I thought studying the notes.h file and its comments was a sufficient
> introduction on how to work with notes in code.

Yeah, I took most of the explanation from notes.h.  But it can be nice
to have the high-level "here are the functions you have to call"
information in one place without hunting around for it.

> This looks like a good start.

Thanks.

Re: [PATCH 04/18] notes.h/c: Propagate combine_notes_fn return value to add_note() and beyond

[Jonathan Nieder]

Johan Herland wrote:

> The combine_notes_fn functions uses a non-zero return value to indicate
> failure. However, this return value was converted to a call to die()
> in note_tree_insert().

For what it's worth, I still like it.

> Instead, propagate this return value out to add_note(), and return it
> from there

It's always odd deciding what to do in the code paths that "can't
happen".  Ideally one would want static analyzers to check that, while
at the same time subjecting the user to some nice graceful fallback
behavior when it happens anyway.

	fatal: confused: combine_notes_overwrite failed

In this case I'm not sure what the message in die() should be, but
it seems sane to die with some message.  Maybe this should be
mentioned in the commit message, though?

Re: [PATCH 07/18] builtin/notes.c: Split notes ref DWIMmery into a separate function

[Jonathan Nieder]

Johan Herland wrote:

> --- a/builtin/notes.c
> +++ b/builtin/notes.c
> @@ -83,6 +83,16 @@ struct msg_arg {
>  	struct strbuf buf;
>  };
>  
> +static void expand_notes_ref(struct strbuf *sb)
> +{
> +	if (!prefixcmp(sb->buf, "refs/notes/"))
> +		return; /* we're happy */
> +	else if (!prefixcmp(sb->buf, "notes/"))
> +		strbuf_insert(sb, 0, "refs/", 5);
> +	else
> +		strbuf_insert(sb, 0, "refs/notes/", 11);
> +}

Aside: I'm not sure this is the most convenient rule to use after all.

Example:

 $ git log --notes-ref=charon/notes/full
 fatal: unrecognized argument: --notes-ref=charon/notes/full
 $ git log --show-notes=charon/notes/full
 warning: notes ref refs/notes/charon/notes/full is invalid
...
 $ git log --show-notes=remotes/charon/notes/full
 warning: notes ref refs/notes/remotes/charon/notes/full is invalid
...
 $ git log --show-notes=refs/remotes/charon/notes/full -1
 commit 16461e8e5fc5b2dbe9176b9a8313c395e1e07304
 Merge: c3e5a06 79bd09f
 Author: Junio C Hamano <gitster@pobox.com>
 Date:   Thu Sep 30 16:02:27 2010 -0700
 
     Merge branch 'il/remote-fd-ext' into pu
     
     * il/remote-fd-ext:
       fixup! git-remote-fd
 
 Notes (remotes/charon/notes/full):
     Pu-Overview:
         What's cooking in git.git (Sep 2010, #07; Wed, 29)
 $

And now that I think of it, the revision args parser uses its own code
for this...

Regardless, this patch is a step in the right direction imho.

Re: [PATCH 03/18] notes.h/c: Clarify the handling of notes objects that are == null_sha1

[Johan Herland]

On Tuesday 5. October 2010 17.21.20 Jonathan Nieder wrote:
> Johan Herland wrote:
> > The only functional changes in this patch concern the handling of
> > null_sha1 in notes_tree_insert(). Otherwise the patch consists solely of
> > reordering functions in notes.c to avoid use-before-declaration
> 
> Would it makes sense to split off that no-op as a separate patch?

Yes. This will be done in the next iteration.

> > --- a/notes.c
> > +++ b/notes.c
> > @@ -175,7 +248,10 @@ static void note_tree_insert(struct notes_tree *t, struct int_node *tree,
> > 
> >  	switch (GET_PTR_TYPE(*p)) {
> >  	
> >  	case PTR_TYPE_NULL:
> >  		assert(!*p);
> > 
> > -		*p = SET_PTR_TYPE(entry, type);
> > +		if (is_null_sha1(entry->val_sha1))
> > +			free(entry);
> > +		else
> > +			*p = SET_PTR_TYPE(entry, type);
> > 
> >  		return;
> >  	
> >  	case PTR_TYPE_NOTE:
> >  		switch (type) {
> 
> No note present, but the node for one is.  This skips insertion of
> empty notes, for consistency with:
> 
> > @@ -191,6 +267,9 @@ static void note_tree_insert(struct notes_tree *t, struct int_node *tree,
> > 
> >  					    sha1_to_hex(l->val_sha1),
> >  					    sha1_to_hex(entry->val_sha1),
> >  					    sha1_to_hex(l->key_sha1));
> > 
> > +
> > +				if (is_null_sha1(l->val_sha1))
> > +					note_tree_remove(t, tree, n, entry);
> 
> The note-present case, where the combine_notes() function can
> return a null sha1 to request that a note be removed.
> 
> >  				free(entry);
> >  				return;
> >  			
> >  			}
> > 
> > @@ -222,6 +301,10 @@ static void note_tree_insert(struct notes_tree *t, struct int_node *tree,
> > 
> >  	/* non-matching leaf_node */
> >  	assert(GET_PTR_TYPE(*p) == PTR_TYPE_NOTE ||
> >  	
> >  	       GET_PTR_TYPE(*p) == PTR_TYPE_SUBTREE);
> > 
> > +	if (is_null_sha1(entry->val_sha1)) { /* skip insertion of empty note */
> > +		free(entry);
> > +		return;
> > +	}
> 
> The more usual no-note-present case.  Again, this skips insertion
> of empty notes.

All correct.

> Do I understand correctly that the point of the main point of
> this patch is to allow combine_notes() functions to request
> that a note be deleted?  If so, it would be nice if the commit
> message said so.

Indeed, that is the main point. I believe the paragraph following the
commit subject did indeed explain this, but I will try to clarify this
further in the next iteration.

> Regardless, for what it's worth,
> Acked-by: Jonathan Nieder <jrnieder@gmail.com>

Thanks,

...Johan


-- 
Johan Herland, <johan@herland.net>
www.herland.net

Re: [PATCH 04/18] notes.h/c: Propagate combine_notes_fn return value to add_note() and beyond

[Johan Herland]

On Tuesday 5. October 2010 17.38.38 Jonathan Nieder wrote:
> Johan Herland wrote:
> > The combine_notes_fn functions uses a non-zero return value to indicate
> > failure. However, this return value was converted to a call to die()
> > in note_tree_insert().
> 
> For what it's worth, I still like it.
> 
> > Instead, propagate this return value out to add_note(), and return it
> > from there
> 
> It's always odd deciding what to do in the code paths that "can't
> happen".  Ideally one would want static analyzers to check that, while
> at the same time subjecting the user to some nice graceful fallback
> behavior when it happens anyway.
> 
> 	fatal: confused: combine_notes_overwrite failed
> 
> In this case I'm not sure what the message in die() should be, but
> it seems sane to die with some message.  Maybe this should be
> mentioned in the commit message, though?

Ok, I've added a paragraph to the commit message mentioning that most of 
add_note()'s callers now implement the die() previously located in 
notes_tree_insert(). Will be in the next iteration.


Thanks,

...Johan


-- 
Johan Herland, <johan@herland.net>
www.herland.net

Test script style (Re: [PATCH 08/18] git notes merge: Initial implementation handling trivial merges only)

[Jonathan Nieder]

Johan Herland wrote:

> This initial implementation of 'git notes merge' only handles the trivial
> merge cases (i.e. where the merge is either a no-op, or a fast-forward).

Mm, sounds like a nice thing to have anyway.

Now to digress: some generalities about test scripts.  This will
probably be very tedious.  I'm writing it as groundwork before
reviewing your test (since I don't feel on solid ground about this
topic at all).

More focused thoughts on other aspects of the patch will follow in a
separate message.

First:

	See http://thread.gmane.org/gmane.comp.version-control.git/155596/focus=155673
	If you don't like what you see, no need to read the rest
	of this message. :)

Motivation:

	Not being the best of shell script readers (or writers,
	for that matter), I need all the help from stylistic cues
	I can get.  Old test scripts have a consistent style
	generally, but newer ones are starting to diverge from
	one another.

A rough test format:

	#!/bin/sh
	#
	# Copyright (c) 2010 ...
	#

	test_description='...
	. ./test-lib.sh
	. ...

	constant data
	function definitions

	setup }
	test  }
	test  } repeat as necessary
	test  }

	test_done

Test description:

	test_description = 'One-line description

	Some words or diagrams describing the invariants (e.g., history)
	maintained between tests'

Constant data:

	Simple commands to produce test vectors, expected output, and
	other variables and files that it might be convenient to have
	unchanged available throughout the test script.

	Because not guarded by a test assertion, this section would
	not include any git commands, nor any commands that might fail
	or write to the terminal.  So: this section might use
	"cat <<\", "mkdir -p", "cp", "cp -R", "mv", "printf", "foo=",
	"unset", and "export", but not much else.

Function definitions:

	Tests can define functions inside a test_expect_success block,
	too, but the generally useful functions would go up front with
	the constant data.

Setup:

	test_expect_success '(setup | set up) ...' '
		Commands to set up for the next batch of tests.
		Can rely on previous setup and can do just about
		anything.
	'

Tests:
	test_expect_success|failure '... some claim...' '
		Commands to test that claim.
		Could do all sorts of things, as long as they do not
		disturb the invariants established by the
		constant_data and setup sections.
	'

What is not present:

	A test in this style would not include any commands except for
	test_done outside a test assertion after the first
	test_expect_success.

This is meant to be a sort of compromise between what t/README says
("Put all code inside test_expect_success and other assertions") and
what people actually do.  I have no problem with people doing
something else --- in fact, some tests would not make any sense in
this style.  In general, if a person is writing maintainable tests
that do not slow down "make test" by much, it does not make much sense
to put new obstacles in her way.

What I expect is that new tests would be easier to read and extend in
this style, since to get started, all a person has to pay attention to
are the setup commands.  So a potential collaborator could say "if you
use this structure, it will make my life easier".

Thoughts?  Would it make sense to eventually put something like this
in t/CodingStyle or nearby?

Re: Test script style (Re: [PATCH 08/18] git notes merge: Initial implementation handling trivial merges only)

[Junio C Hamano]

Jonathan Nieder <jrnieder@gmail.com> writes:

> Thoughts?  Would it make sense to eventually put something like this
> in t/CodingStyle or nearby?

> Tests:
> 	test_expect_success|failure '... some claim...' '
> 		Commands to test that claim.
> 		Could do all sorts of things, as long as they do not
> 		disturb the invariants established by the
> 		constant_data and setup sections.
> 	'

In practice, I am afraid it would take a lot more discipline than any of
the current test script does to actually preserve the invariants.  But if
we can arrange that, it would be ideal.  For one thing, it would finally
make the subtest skip feature of GIT_SKIP_TESTS usable.

An obvious way to do so would be

 Tests:
 	test_expect_success|failure '... some claim...' '
+ 		Commands to establish a known precondition without
+		depending on the state left by previous steps.
 		Commands to test that claim.
-		Could do all sorts of things, as long as they do not
-		disturb the invariants established by the
-		constant_data and setup sections.
 	'

but if done naively, the time it takes to re-establish a known
precondition for each and every test would add up to substantial
overhead.

Re: [PATCH 08/18] git notes merge: Initial implementation handling trivial merges only

[Jonathan Nieder]

Johan Herland wrote:

> This initial implementation of 'git notes merge' only handles the trivial
> merge cases (i.e. where the merge is either a no-op, or a fast-forward).

This alone should already be a nice UI improvement: in the
fast-forward case, with this patch applied, in place of

	git fetch . refs/notes/x:refs/notes/commits

one could write

	git notes merge x

This reminds me: it would be nice if non-builtin scripts could use

	git notes --get-notes-ref $refarg

to learn the configured notes ref.  In other words, shouldn't the
default_notes_ref() exposed in patch 2 also be exposed to scripted
callers?  If someone else doesn't get around to it, I can mock
something up in the next few days.

[...]
> +++ b/notes-merge.h
> @@ -0,0 +1,30 @@
> +#ifndef NOTES_MERGE_H
> +#define NOTES_MERGE_H
> +
> +struct notes_merge_options {
> +	const char *local_ref;
> +	const char *remote_ref;
> +	int verbosity;
> +};
> +
> +void init_notes_merge_options(struct notes_merge_options *o);
[...]
> +int notes_merge(struct notes_merge_options *o,
> +		unsigned char *result_sha1);

So the command is usable as-is from other builtins.  Nice.

> +++ b/notes-merge.c
> @@ -0,0 +1,103 @@
[...]
> +#include "cache.h"
> +#include "commit.h"
> +#include "notes-merge.h"
> +
> +void init_notes_merge_options(struct notes_merge_options *o)
> +{
> +	memset(o, 0, sizeof(struct notes_merge_options));
> +	o->verbosity = 2;
> +}
> +
> +static int show(struct notes_merge_options *o, int v)
> +{
> +	return (o->verbosity >= v) || o->verbosity >= 5;
> +}

Should the verbosities be of enum type?

	enum notes_merge_verbosity {
		DEFAULT_VERBOSITY = 2,
		MAX_VERBOSITY = 5,
		etc
	};

> +
> +#define OUTPUT(o, v, ...) \
> +	do { if (show((o), (v))) { printf(__VA_ARGS__); puts(""); } } while (0)

I would find it easier to read

	if (o->verbosity >= DEFAULT_VERBOSITY)
		fprintf(stderr, ...)

unless there are going to be a huge number of messages.

> +
> +int notes_merge(struct notes_merge_options *o,
> +		unsigned char *result_sha1)
> +{
> +	unsigned char local_sha1[20], remote_sha1[20];
> +	struct commit *local, *remote;
> +	struct commit_list *bases = NULL;
> +	const unsigned char *base_sha1;
> +	int result = 0;
> +
> +	hashclr(result_sha1);
> +
> +	OUTPUT(o, 5, "notes_merge(o->local_ref = %s, o->remote_ref = %s)",
> +	       o->local_ref, o->remote_ref);

Would trace_printf be a good fit for messages like this one?  If not,
any idea about how it could be made to fit some day?

(It is especially nice to be able to direct the trace somewhere other
than stdout and stderr when running tests.)

> +
> +	if (!o->local_ref || get_sha1(o->local_ref, local_sha1)) {
> +		/* empty notes ref => assume empty notes tree */

Can an empty ref be distinguished from a missing ref?  It would be
nice to error out when breakage is detected.

[...]
> +	/* Find merge bases */
> +	bases = get_merge_bases(local, remote, 1);
> +	if (!bases) {
> +		base_sha1 = null_sha1;
> +		OUTPUT(o, 4, "No merge base found; doing history-less merge");
> +	} else if (!bases->next) {
> +		base_sha1 = bases->item->object.sha1;
> +		OUTPUT(o, 4, "One merge base found (%.7s)",
> +		       sha1_to_hex(base_sha1));
> +	} else {
> +		/* TODO: How to handle multiple merge-bases? */

With a recursive merge of the ancestors, of course. :)

The difficult part is what to do when a merge of ancestors results in
conflicts.

[...]
> +++ b/builtin/notes.c
> @@ -772,6 +779,50 @@ static int show(int argc, const char **argv, const char *prefix)
>  	return retval;
>  }
>  
> +static int merge(int argc, const char **argv, const char *prefix)
> +{
> +	struct strbuf remote_ref = STRBUF_INIT, msg = STRBUF_INIT;
> +	unsigned char result_sha1[20];
> +	struct notes_merge_options o;
> +	int verbosity = 0, result;
> +	struct option options[] = {
> +		OPT__VERBOSITY(&verbosity),
> +		OPT_END()
> +	};
> +
> +	argc = parse_options(argc, argv, prefix, options,
> +			     git_notes_merge_usage, 0);
> +
> +	if (argc != 1) {
> +		error("Must specify a notes ref to merge");
> +		usage_with_options(git_notes_merge_usage, options);
> +	}
> +
> +	init_notes_merge_options(&o);
> +	o.verbosity = verbosity + 2; // default verbosity level is 2

Maybe

	o.verbosity += verbosity;

or

	o.verbosity = DEFAULT_NOTES_MERGE_VERBOSITY + verbosity;

to allow the default verbosity to be set in one place?

> +	o.local_ref = default_notes_ref();
> +	strbuf_addstr(&remote_ref, argv[0]);
> +	expand_notes_ref(&remote_ref);
> +	o.remote_ref = remote_ref.buf;
> +
> +	result = notes_merge(&o, result_sha1);
> +
> +	strbuf_addf(&msg, "notes: Merged notes from %s into %s",
> +		    remote_ref.buf, default_notes_ref());
> +	if (result == 0) { /* Merge resulted (trivially) in result_sha1 */
> +		/* Update default notes ref with new commit */
> +		update_ref(msg.buf, default_notes_ref(), result_sha1, NULL,
> +			   0, DIE_ON_ERR);
> +	} else {
> +		/* TODO: */
> +		die("'git notes merge' cannot yet handle non-trivial merges!");

Mm.  In the long run, will (result != 0) mean "merge conflict"?

> @@ -865,6 +916,8 @@ int cmd_notes(int argc, const char **argv, const char *prefix)
>  		result = append_edit(argc, argv, prefix);
>  	else if (!strcmp(argv[0], "show"))
>  		result = show(argc, argv, prefix);
> +	else if (!strcmp(argv[0], "merge"))
> +		result = merge(argc, argv, prefix);

Thanks for a pleasant read.

Re: [PATCH 07/18] builtin/notes.c: Split notes ref DWIMmery into a separate function

[Johan Herland]

On Tuesday 5. October 2010 17.50.53 Jonathan Nieder wrote:
> Johan Herland wrote:
> > +static void expand_notes_ref(struct strbuf *sb)
> > +{
> > +	if (!prefixcmp(sb->buf, "refs/notes/"))
> > +		return; /* we're happy */
> > +	else if (!prefixcmp(sb->buf, "notes/"))
> > +		strbuf_insert(sb, 0, "refs/", 5);
> > +	else
> > +		strbuf_insert(sb, 0, "refs/notes/", 11);
> > +}
> 
> Aside: I'm not sure this is the most convenient rule to use after all.

FTR, that rule is not introduced by this patch, the patch merely moves it into 
a separate function.

> Example:
> 
>  $ git log --notes-ref=charon/notes/full
>  fatal: unrecognized argument: --notes-ref=charon/notes/full
>  $ git log --show-notes=charon/notes/full
>  warning: notes ref refs/notes/charon/notes/full is invalid
> ...
>  $ git log --show-notes=remotes/charon/notes/full
>  warning: notes ref refs/notes/remotes/charon/notes/full is invalid
> ...
>  $ git log --show-notes=refs/remotes/charon/notes/full -1
>  commit 16461e8e5fc5b2dbe9176b9a8313c395e1e07304
>  Merge: c3e5a06 79bd09f
>  Author: Junio C Hamano <gitster@pobox.com>
>  Date:   Thu Sep 30 16:02:27 2010 -0700
> 
>      Merge branch 'il/remote-fd-ext' into pu
> 
>      * il/remote-fd-ext:
>        fixup! git-remote-fd
> 
>  Notes (remotes/charon/notes/full):
>      Pu-Overview:
>          What's cooking in git.git (Sep 2010, #07; Wed, 29)
>  $

Indeed, if you keep notes refs outside refs/notes, the current behaviour is 
not very user-friendly. So far, we've required all notes refs to be within 
refs/notes. (See for example init_notes_check() in builtin/notes.c, which 
refuses to work with notes refs outside 'refs/notes/', hence was probably the 
reason for adding the above code in the first place.)

I guess this moves us towards the discussion of how to handle remote notes 
refs and how to synchronize them on fetch/push. In short, if we want to keep 
notes refs outside of refs/notes (e.g. in refs/remotes/foo/notes), we need to 
change this part of the code.

> And now that I think of it, the revision args parser uses its own code
> for this...

I assuming you're talking about the revision args parser's DWIMing of "foo" 
into the first existing ref in the following list:

1. $GIT_DIR/foo
2. refs/foo
3. refs/tags/foo
4. refs/heads/foo
5. refs/remotes/foo
6. refs/remotes/foo/HEAD

If we want to reuse this DWIMery, we obviously want a different list of "auto-
completions". Maybe something like:

1. refs/notes/foo
2. refs/remote-notes/foo (depends on how we organize remote notes refs)
3. ?

> Regardless, this patch is a step in the right direction imho.

Thanks, I expect future patches to change this code in order to deal with 
remote notes refs. For the purposes of the current patch series, I will assume 
that all notes refs live under refs/notes.


...Johan

-- 
Johan Herland, <johan@herland.net>
www.herland.net

Re: [PATCH 08/18] git notes merge: Initial implementation handling trivial merges only

[Johan Herland]

On Thursday 7. October 2010 08.24.33 Jonathan Nieder wrote:
> Johan Herland wrote:
> > This initial implementation of 'git notes merge' only handles the trivial
> > merge cases (i.e. where the merge is either a no-op, or a fast-forward).
> 
> [...]
> 
> This reminds me: it would be nice if non-builtin scripts could use
> 
> 	git notes --get-notes-ref $refarg
> 
> to learn the configured notes ref.  In other words, shouldn't the
> default_notes_ref() exposed in patch 2 also be exposed to scripted
> callers?

I agree, but I'd like to name it 'git notes get-ref' instead, to stay
consistent with the current subcommand (instead of option) design.

> If someone else doesn't get around to it, I can mock
> something up in the next few days.

There is a patch implementing 'git notes get-ref' in the next iteration
of this series. :)

> > +++ b/notes-merge.h
> > @@ -0,0 +1,30 @@
> > +#ifndef NOTES_MERGE_H
> > +#define NOTES_MERGE_H
> > +
> > +struct notes_merge_options {
> > +	const char *local_ref;
> > +	const char *remote_ref;
> > +	int verbosity;
> > +};
> > +
> > +void init_notes_merge_options(struct notes_merge_options *o);
> 
> [...]
> 
> > +int notes_merge(struct notes_merge_options *o,
> > +		unsigned char *result_sha1);
> 
> So the command is usable as-is from other builtins.  Nice.

Yep, that's the idea. notes-merge.h is really only an extension of
notes.h for providing the merge-related functionality.

> > +++ b/notes-merge.c
> > @@ -0,0 +1,103 @@
> 
> [...]
> 
> > +void init_notes_merge_options(struct notes_merge_options *o)
> > +{
> > +	memset(o, 0, sizeof(struct notes_merge_options));
> > +	o->verbosity = 2;
> > +}
> > +
> > +static int show(struct notes_merge_options *o, int v)
> > +{
> > +	return (o->verbosity >= v) || o->verbosity >= 5;
> > +}
> 
> Should the verbosities be of enum type?
> 
> 	enum notes_merge_verbosity {
> 		DEFAULT_VERBOSITY = 2,
> 		MAX_VERBOSITY = 5,
> 		etc
> 	};

Maybe. I've added these constants and used them where it made sense
(to me) in the next iteration.

> > +
> > +#define OUTPUT(o, v, ...) \
> > +	do { if (show((o), (v))) { printf(__VA_ARGS__); puts(""); } } while (0)
> 
> I would find it easier to read
> 
> 	if (o->verbosity >= DEFAULT_VERBOSITY)
> 		fprintf(stderr, ...)
> 
> unless there are going to be a huge number of messages.

The current version is modeled on the show() and output() functions in
merge-recursive.c. I think that works better in this situation.
Or maybe you have a better solution for merge-recursive.c as well?

> > +
> > +int notes_merge(struct notes_merge_options *o,
> > +		unsigned char *result_sha1)
> > +{
> > +	unsigned char local_sha1[20], remote_sha1[20];
> > +	struct commit *local, *remote;
> > +	struct commit_list *bases = NULL;
> > +	const unsigned char *base_sha1;
> > +	int result = 0;
> > +
> > +	hashclr(result_sha1);
> > +
> > +	OUTPUT(o, 5, "notes_merge(o->local_ref = %s, o->remote_ref = %s)",
> > +	       o->local_ref, o->remote_ref);
> 
> Would trace_printf be a good fit for messages like this one?  If not,
> any idea about how it could be made to fit some day?
> 
> (It is especially nice to be able to direct the trace somewhere other
> than stdout and stderr when running tests.)

Agreed. The OUTPUT(o, 5, ...) instances should use trace_printf()
instead. Fixed in the next iteration.

> > +
> > +	if (!o->local_ref || get_sha1(o->local_ref, local_sha1)) {
> > +		/* empty notes ref => assume empty notes tree */
> 
> Can an empty ref be distinguished from a missing ref?  It would be
> nice to error out when breakage is detected.

I'm not sure when you think we should (or shouldn't) error out. FWIW,
I've modeled the current code on what 'git merge' does. See [1] for
more details.

> > +	/* Find merge bases */
> > +	bases = get_merge_bases(local, remote, 1);
> > +	if (!bases) {
> > +		base_sha1 = null_sha1;
> > +		OUTPUT(o, 4, "No merge base found; doing history-less merge");
> > +	} else if (!bases->next) {
> > +		base_sha1 = bases->item->object.sha1;
> > +		OUTPUT(o, 4, "One merge base found (%.7s)",
> > +		       sha1_to_hex(base_sha1));
> > +	} else {
> > +		/* TODO: How to handle multiple merge-bases? */
> 
> With a recursive merge of the ancestors, of course. :)
> 
> The difficult part is what to do when a merge of ancestors results in
> conflicts.

Exactly. I feel notes merge conflicts are confusing enough to the
average user, and I'd rather not expose them to resolving conflicts in
_recursive_ notes merges...

I guess this becomes a discussion of whether we should model notes
merges on the 'resolve' merge strategy or the 'recursive' merge
strategy. Without having studied each strategy in-depth, I don't know
how much "better" 'recursive' is than 'resolve', especially not from
the POV of notes merges. Are there features of 'recursive' that are
useful to notes merges?

(All I know of the effectual differences between 'resolve' and
'recursive' is the hand waving on the 'git merge' man page:
  "...has been reported to result in fewer merge conflicts without
   causing mis-merges by tests done on actual merge commits taken from
   Linux 2.6 kernel development history.")

In conclusion, if someone can show that's it's worth implementing
recursive notes merging, then I'll gladly do it, but until then I'll
stick with the simplicity of using the first merge base.

> > +++ b/builtin/notes.c
> > @@ -772,6 +779,50 @@ static int show(int argc, const char **argv, const
> > +static int merge(int argc, const char **argv, const char *prefix)
> > +{
> > [...]
> > +	o.verbosity = verbosity + 2; // default verbosity level is 2
> 
> Maybe
> 
> 	o.verbosity += verbosity;
> 
> or
> 
> 	o.verbosity = DEFAULT_NOTES_MERGE_VERBOSITY + verbosity;
> 
> to allow the default verbosity to be set in one place?

Agreed. Fixed in the next iteration.

> > +	result = notes_merge(&o, result_sha1);
> > +
> > +	strbuf_addf(&msg, "notes: Merged notes from %s into %s",
> > +		    remote_ref.buf, default_notes_ref());
> > +	if (result == 0) { /* Merge resulted (trivially) in result_sha1 */
> > +		/* Update default notes ref with new commit */
> > +		update_ref(msg.buf, default_notes_ref(), result_sha1, NULL,
> > +			   0, DIE_ON_ERR);
> > +	} else {
> > +		/* TODO: */
> > +		die("'git notes merge' cannot yet handle non-trivial merges!");
> 
> Mm.  In the long run, will (result != 0) mean "merge conflict"?

Almost. If you look at the notes_merge() docs in notes-merge.h by the
end of this series, you'll see the following return values:

0: Merge trivially succeeded in an existing commit (e.g. fast-forward).

1: Merge successfully completes a merge commit (i.e. no conflicts).

-1: Merge results is conflicts.

> Thanks for a pleasant read.

Thanks for reading! :)


...Johan


[1]: Let's analyze the different cases here:

1. local_ref ("our" side of the merge) doesn't exist
(i.e. an unborn notes ref):

In this situation 'git merge' simply creates local_ref to point at
remote_ref. 'git notes merge' does the same.


2. local_ref is empty (.git/refs/notes/$local_ref is an empty file):

'git merge' fails with
  error: unable to resolve reference HEAD: No such file or directory
  fatal: Cannot lock the ref 'HEAD'.

'git notes merge' fails with
  error: unable to resolve reference refs/notes/$local_ref: No such file or directory
  fatal: Cannot lock the ref 'refs/notes/$local_ref'.

3. local_ref refers to a non-existing commit:

'git merge' fails with
  error: Could not read $non_existing_sha1
  error: Trying to write ref ORIG_HEAD with nonexistant object $non_existing_sha1
  fatal: Cannot update the ref 'ORIG_HEAD'.
  fatal: bad object HEAD

'git notes merge' fails with
  fatal: Failed to read notes tree referenced by refs/notes/$local_ref ($non_existing_sha1)

4. local_ref refers to a non-commit (tree or blob):

'git merge' fails with
  error: Object $tree_sha1 is a tree, not a commit
  error: Object $tree_sha1 is a tree, not a commit
  Segmentation fault (someone might want to look into this...)

'git notes merge' fails with
  error: Object $tree_sha1 is a tree, not a commit
  fatal: Could not parse commit 'refs/notes/$local_ref.

Looking at remote_ref instead:

5. remote_ref ("their" side of the merge) doesn't exist
(i.e. an unborn notes ref):

'git merge' fails with:
  fatal: '$remote_ref' does not point to a commit

'git notes merge' fails with:
  fatal: Could not parse commit 'refs/notes/$remote_ref'.

6. remote_ref is empty (.git/refs/notes/$remote_ref is an empty file):

same as #5

7. remote_ref refers to a non-existing commit:

same as #5

8. remote_ref refers to a non-commit (tree or blob):

'git merge' fails with
  error: $remote_ref: expected commit type, but the object dereferences to tree type
  fatal: '$remote_ref' does not point to a commit

'git notes merge' fails with
  error: Object $tree_sha1 is a tree, not a commit
  fatal: Could not parse commit '$remote_ref'.

I believe all these outcomes make sense.

-- 
Johan Herland, <johan@herland.net>
www.herland.net

Re: [PATCH 08/18] git notes merge: Initial implementation handling trivial merges only

[Jonathan Nieder]

Johan Herland wrote:

> I agree, but I'd like to name it 'git notes get-ref' instead, to stay
> consistent with the current subcommand (instead of option) design.

Sounds good. :)

> Jonathan Nieder wrote:

>> I would find it easier to read
>>
>> 	if (o->verbosity >= DEFAULT_VERBOSITY)
>> 		fprintf(stderr, ...)
>>
>> unless there are going to be a huge number of messages.
>
> The current version is modeled on the show() and output() functions in
> merge-recursive.c. I think that works better in this situation.
> Or maybe you have a better solution for merge-recursive.c as well?

Hmm --- isn't the point of output() that it indents to the appropriate
level to portray a recursive merge?

Similarly, show() prevents those confusing messages from the internal
merge between ancestors from being printed when the user is not
interested.

But if you think they are important abstractions to maintain, I won't
stop you. :)

>>> +
>>> +	if (!o->local_ref || get_sha1(o->local_ref, local_sha1)) {
>>> +		/* empty notes ref => assume empty notes tree */
[...]
> I'm not sure when you think we should (or shouldn't) error out.

get_sha1() can return -1 in the following cases:

 - starts with :/, regex does not match.
 - starts with :, entry not present in index
 - in form <rev>:<path>, <path> does not exist in <rev>
 - in form <rev>^, <rev> does not exist or that parent does not
   exist
 - tag being used as commit points to a tree instead
 - et c.

Especially if the caller tries

	git notes merge 'afjkdlsa^{gobbledeegook'

I would not like the merge to succeed.

So as I see it, there are four cases:

 - get_sha1() succeeds and returns a commit ==> merge that rev
 - get_sha1() succeeds and returns a non-commit ==> fail
 - get_sha1() fails, but resolve_ref() indicates a ref valid
   for writing ==> merge empty tree
 - get_sha1() fails, invalid refname ==> fail

The current code does not notice case 4, does it?

> I guess this becomes a discussion of whether we should model notes
> merges on the 'resolve' merge strategy or the 'recursive' merge
> strategy. Without having studied each strategy in-depth, I don't know
> how much "better" 'recursive' is than 'resolve', especially not from
> the POV of notes merges.

I think 'resolve' should be good enough for now.  We can always add
'recursive' later.

The cases where 'recursive' might help are those in which both sides
made a lot of changes to the same notes.  It helps in two ways:
signaling conflicts that might have been otherwise missed and merging
cleanly in cases that might otherwise produce spurious conflicts.
In theory, it makes the result less "arbitrary"; in practice, it seems
to help avoid some conflicts in ugly cases like merging one week's pu
with the next week's pu.

[...]
> Almost. If you look at the notes_merge() docs in notes-merge.h by the
> end of this series, you'll see the following return values:
> 
> 0: Merge trivially succeeded in an existing commit (e.g. fast-forward).
> 
> 1: Merge successfully completes a merge commit (i.e. no conflicts).
> 
> -1: Merge results is conflicts.

What kind of caller would care about the distinction between 1 and -1
here (just curious)?

Jonathan

Re: [PATCH 08/18] git notes merge: Initial implementation handling trivial merges only

[Johan Herland]

On Saturday 09 October 2010, Jonathan Nieder wrote:
> Johan Herland wrote:
> > Jonathan Nieder wrote:
> >> I would find it easier to read
> >> 
> >> 	if (o->verbosity >= DEFAULT_VERBOSITY)
> >> 	
> >> 		fprintf(stderr, ...)
> >> 
> >> unless there are going to be a huge number of messages.
> > 
> > The current version is modeled on the show() and output() functions in
> > merge-recursive.c. I think that works better in this situation.
> > Or maybe you have a better solution for merge-recursive.c as well?
> 
> Hmm --- isn't the point of output() that it indents to the appropriate
> level to portray a recursive merge?
> 
> Similarly, show() prevents those confusing messages from the internal
> merge between ancestors from being printed when the user is not
> interested.
> 
> But if you think they are important abstractions to maintain, I won't
> stop you. :)

I see. I still find the OUTPUT() macro more readable, but I've amended
the patch to eliminate the extraneous show() function. Hence, you'll
find this in the next iteration:

#define OUTPUT(o, v, ...) \
	do { \
		if ((o)->verbosity >= (v)) { \
			printf(__VA_ARGS__); \
			puts(""); \
		} \
	} while (0)

> >>> +
> >>> +	if (!o->local_ref || get_sha1(o->local_ref, local_sha1)) {
> >>> +		/* empty notes ref => assume empty notes tree */
> 
> [...]
> 
> > I'm not sure when you think we should (or shouldn't) error out.
> 
> get_sha1() can return -1 in the following cases:
> 
>  - starts with :/, regex does not match.
>  - starts with :, entry not present in index
>  - in form <rev>:<path>, <path> does not exist in <rev>
>  - in form <rev>^, <rev> does not exist or that parent does not
>    exist
>  - tag being used as commit points to a tree instead
>  - et c.

I see. I didn't take these into account when I wrote the code.

> Especially if the caller tries
> 
> 	git notes merge 'afjkdlsa^{gobbledeegook'
> 
> I would not like the merge to succeed.

Agreed, but I believe that command currently returns:

  fatal: Could not parse commit 'refs/notes/afjkdlsa^{gobbledeegook'.

(or using afjkdlsa^{gobbledeegook as "our" side of the merge):

  fatal: Cannot lock the ref 'refs/notes/afjkdlsa^{gobbledeegook'.

> So as I see it, there are four cases:
> 
>  - get_sha1() succeeds and returns a commit ==> merge that rev
>  - get_sha1() succeeds and returns a non-commit ==> fail
>  - get_sha1() fails, but resolve_ref() indicates a ref valid
>    for writing ==> merge empty tree
>  - get_sha1() fails, invalid refname ==> fail
> 
> The current code does not notice case 4, does it?

My tests indicate that case 4 does fail (correctly). However I also
agree that this is not at all clear from the current code, so I've
rewritten this code to something that is hopefully more straightforward
(this is the next iteration):

	/* Dereference o->local_ref into local_sha1 */
	if (!resolve_ref(o->local_ref, local_sha1, 0, NULL))
		die("Failed to resolve local notes ref '%s'", o->local_ref);
	else if (!check_ref_format(o->local_ref) && is_null_sha1(local_sha1))
		local = NULL; /* local_sha1 == null_sha1 indicates unborn ref */
	else if (!(local = lookup_commit_reference(local_sha1)))
		die("Could not parse local commit %s (%s)",
		    sha1_to_hex(local_sha1), o->local_ref);
	trace_printf("\tlocal commit: %.7s\n", sha1_to_hex(local_sha1));

	/* Dereference o->remote_ref into remote_sha1 */
	if (get_sha1(o->remote_ref, remote_sha1)) {
		/*
		 * Failed to get remote_sha1. If o->remote_ref looks like an
		 * unborn ref, perform the merge using an empty notes tree.
		 */
		if (!check_ref_format(o->remote_ref)) {
			hashclr(remote_sha1);
			remote = NULL;
		}
		else
			die("Failed to resolve remote notes ref '%s'",
			    o->remote_ref);
	}
	else if (!(remote = lookup_commit_reference(remote_sha1)))
		die("Could not parse remote commit %s (%s)",
		    sha1_to_hex(remote_sha1), o->remote_ref);
	trace_printf("\tremote commit: %.7s\n", sha1_to_hex(remote_sha1));

I've also added more testcases for expected failures.

> > I guess this becomes a discussion of whether we should model notes
> > merges on the 'resolve' merge strategy or the 'recursive' merge
> > strategy. Without having studied each strategy in-depth, I don't know
> > how much "better" 'recursive' is than 'resolve', especially not from
> > the POV of notes merges.
> 
> I think 'resolve' should be good enough for now.  We can always add
> 'recursive' later.

My thoughts exactly.

> > If you look at the notes_merge() docs in notes-merge.h by the
> > end of this series, you'll see the following return values:
> > 
> > 0: Merge trivially succeeded in an existing commit (e.g. fast-forward).
> > 
> > 1: Merge successfully completes a merge commit (i.e. no conflicts).
> > 
> > -1: Merge results is conflicts.
> 
> What kind of caller would care about the distinction between 1 and -1
> here (just curious)?

Any caller who cares about the merge at all, I'd imagine

If 1 (or 0) the merge is complete, and there's nothing more to be done
(expect updating the notes ref, of course).

If -1, there are conflicts checked out in .git/NOTES_MERGE_WORKTREE,
and the user must be told to fix them and commit the conflict
resolution.

See the last part of builtin/notes.c:merge() at the end of this series
for an example.


...Johan

-- 
Johan Herland, <johan@herland.net>
www.herland.net