[PATCH v21 00/19] Use ref transactions

[PATCH v21 00/19] Use ref transactions

[Ronnie Sahlberg]

List, Jun

Here is a resend of the first part of the ref transactions patches.
This new series consists of the first 19 patches in the series and
have been reviewed by mhagger.
This series should be good to go now.

I will resend the remaining part of the series separately once I have addressed
Michaels concerns.


Version 21:
 -- split the patch series in two. These are the first 19 patches that
    are now reviewed by mhagger.

Ronnie Sahlberg (19):
  refs.c: remove ref_transaction_rollback
  refs.c: ref_transaction_commit should not free the transaction
  refs.c: constify the sha arguments for
    ref_transaction_create|delete|update
  refs.c: allow passing NULL to ref_transaction_free
  refs.c: add a strbuf argument to ref_transaction_commit for error
    logging
  lockfile.c: add a new public function unable_to_lock_message
  lockfile.c: make lock_file return a meaningful errno on failure
  refs.c: add an err argument to repack_without_refs
  refs.c: make sure log_ref_setup returns a meaningful errno
  refs.c: verify_lock should set errno to something meaningful
  refs.c: make remove_empty_directories always set errno to something
    sane
  refs.c: commit_packed_refs to return a meaningful errno on failure
  refs.c: make resolve_ref_unsafe set errno to something meaningful on
    error
  refs.c: log_ref_write should try to return meaningful errno
  refs.c: make ref_update_reject_duplicates take a strbuf argument for
    errors
  refs.c: make update_ref_write update a strbuf on failure
  update-ref: use err argument to get error from ref_transaction_commit
  refs.c: remove the onerr argument to ref_transaction_commit
  refs.c: change ref_transaction_update() to do error checking and
    return status

 builtin/remote.c     |   5 +-
 builtin/update-ref.c |  20 +++---
 cache.h              |   4 +-
 lockfile.c           |  39 ++++++-----
 refs.c               | 178 ++++++++++++++++++++++++++++++++++++---------------
 refs.h               |  53 +++++++++------
 6 files changed, 199 insertions(+), 100 deletions(-)

-- 
2.0.1.546.gf603308

[PATCH v21 01/19] refs.c: remove ref_transaction_rollback

[Ronnie Sahlberg]

We do not yet need both a rollback and a free function for transactions.
Remove ref_transaction_rollback and use ref_transaction_free instead.

At a later stage we may reintroduce a rollback function if we want to start
adding reusable transactions and similar.

Reviewed-by: Jonathan Nieder <jrnieder@gmail.com>
Reviewed-by: Michael Haggerty <mhagger@alum.mit.edu>
Signed-off-by: Ronnie Sahlberg <sahlberg@google.com>
---
 refs.c |  7 +------
 refs.h | 16 +++++++---------
 2 files changed, 8 insertions(+), 15 deletions(-)

diff --git a/refs.c b/refs.c
index dc45774..6d841a0 100644
--- a/refs.c
+++ b/refs.c
@@ -3334,7 +3334,7 @@ struct ref_transaction *ref_transaction_begin(void)
 	return xcalloc(1, sizeof(struct ref_transaction));
 }
 
-static void ref_transaction_free(struct ref_transaction *transaction)
+void ref_transaction_free(struct ref_transaction *transaction)
 {
 	int i;
 
@@ -3345,11 +3345,6 @@ static void ref_transaction_free(struct ref_transaction *transaction)
 	free(transaction);
 }
 
-void ref_transaction_rollback(struct ref_transaction *transaction)
-{
-	ref_transaction_free(transaction);
-}
-
 static struct ref_update *add_update(struct ref_transaction *transaction,
 				     const char *refname)
 {
diff --git a/refs.h b/refs.h
index 4e3050d..cfd1832 100644
--- a/refs.h
+++ b/refs.h
@@ -219,18 +219,12 @@ enum action_on_err {
 
 /*
  * Begin a reference transaction.  The reference transaction must
- * eventually be commited using ref_transaction_commit() or rolled
- * back using ref_transaction_rollback().
+ * eventually be commited using ref_transaction_commit() or freed by
+ * calling ref_transaction_free().
  */
 struct ref_transaction *ref_transaction_begin(void);
 
 /*
- * Roll back a ref_transaction and free all associated data.
- */
-void ref_transaction_rollback(struct ref_transaction *transaction);
-
-
-/*
  * The following functions add a reference check or update to a
  * ref_transaction.  In all of them, refname is the name of the
  * reference to be affected.  The functions make internal copies of
@@ -238,7 +232,6 @@ void ref_transaction_rollback(struct ref_transaction *transaction);
  * can be REF_NODEREF; it is passed to update_ref_lock().
  */
 
-
 /*
  * Add a reference update to transaction.  new_sha1 is the value that
  * the reference should have after the update, or zeros if it should
@@ -280,6 +273,11 @@ void ref_transaction_delete(struct ref_transaction *transaction,
 int ref_transaction_commit(struct ref_transaction *transaction,
 			   const char *msg, enum action_on_err onerr);
 
+/*
+ * Free an existing transaction and all associated data.
+ */
+void ref_transaction_free(struct ref_transaction *transaction);
+
 /** Lock a ref and then write its file */
 int update_ref(const char *action, const char *refname,
 		const unsigned char *sha1, const unsigned char *oldval,
-- 
2.0.1.546.gf603308

[PATCH v21 02/19] refs.c: ref_transaction_commit should not free the transaction

[Ronnie Sahlberg]

Reviewed-by: Jonathan Nieder <jrnieder@gmail.com>
Reviewed-by: Michael Haggerty <mhagger@alum.mit.edu>
Signed-off-by: Ronnie Sahlberg <sahlberg@google.com>
---
 builtin/update-ref.c | 1 +
 refs.c               | 1 -
 refs.h               | 5 ++---
 3 files changed, 3 insertions(+), 4 deletions(-)

diff --git a/builtin/update-ref.c b/builtin/update-ref.c
index 405267f..1fd7a89 100644
--- a/builtin/update-ref.c
+++ b/builtin/update-ref.c
@@ -369,6 +369,7 @@ int cmd_update_ref(int argc, const char **argv, const char *prefix)
 		update_refs_stdin();
 		ret = ref_transaction_commit(transaction, msg,
 					     UPDATE_REFS_DIE_ON_ERR);
+		ref_transaction_free(transaction);
 		return ret;
 	}
 
diff --git a/refs.c b/refs.c
index 6d841a0..d9cac6d 100644
--- a/refs.c
+++ b/refs.c
@@ -3509,7 +3509,6 @@ cleanup:
 		if (updates[i]->lock)
 			unlock_ref(updates[i]->lock);
 	free(delnames);
-	ref_transaction_free(transaction);
 	return ret;
 }
 
diff --git a/refs.h b/refs.h
index cfd1832..7d946f6 100644
--- a/refs.h
+++ b/refs.h
@@ -219,8 +219,7 @@ enum action_on_err {
 
 /*
  * Begin a reference transaction.  The reference transaction must
- * eventually be commited using ref_transaction_commit() or freed by
- * calling ref_transaction_free().
+ * be freed by calling ref_transaction_free().
  */
 struct ref_transaction *ref_transaction_begin(void);
 
@@ -268,7 +267,7 @@ void ref_transaction_delete(struct ref_transaction *transaction,
 /*
  * Commit all of the changes that have been queued in transaction, as
  * atomically as possible.  Return a nonzero value if there is a
- * problem.  The ref_transaction is freed by this function.
+ * problem.
  */
 int ref_transaction_commit(struct ref_transaction *transaction,
 			   const char *msg, enum action_on_err onerr);
-- 
2.0.1.546.gf603308

[PATCH v21 03/19] refs.c: constify the sha arguments for ref_transaction_create|delete|update

[Ronnie Sahlberg]

ref_transaction_create|delete|update has no need to modify the sha1
arguments passed to it so it should use const unsigned char* instead
of unsigned char*.

Some functions, such as fast_forward_to(), already have its old/new
sha1 arguments as consts. This function will at some point need to
use ref_transaction_update() in which case this change is required.

Reviewed-by: Jonathan Nieder <jrnieder@gmail.com>
Reviewed-by: Michael Haggerty <mhagger@alum.mit.edu>
Signed-off-by: Ronnie Sahlberg <sahlberg@google.com>
---
 refs.c | 7 ++++---
 refs.h | 7 ++++---
 2 files changed, 8 insertions(+), 6 deletions(-)

diff --git a/refs.c b/refs.c
index d9cac6d..21ed465 100644
--- a/refs.c
+++ b/refs.c
@@ -3359,7 +3359,8 @@ static struct ref_update *add_update(struct ref_transaction *transaction,
 
 void ref_transaction_update(struct ref_transaction *transaction,
 			    const char *refname,
-			    unsigned char *new_sha1, unsigned char *old_sha1,
+			    const unsigned char *new_sha1,
+			    const unsigned char *old_sha1,
 			    int flags, int have_old)
 {
 	struct ref_update *update = add_update(transaction, refname);
@@ -3373,7 +3374,7 @@ void ref_transaction_update(struct ref_transaction *transaction,
 
 void ref_transaction_create(struct ref_transaction *transaction,
 			    const char *refname,
-			    unsigned char *new_sha1,
+			    const unsigned char *new_sha1,
 			    int flags)
 {
 	struct ref_update *update = add_update(transaction, refname);
@@ -3387,7 +3388,7 @@ void ref_transaction_create(struct ref_transaction *transaction,
 
 void ref_transaction_delete(struct ref_transaction *transaction,
 			    const char *refname,
-			    unsigned char *old_sha1,
+			    const unsigned char *old_sha1,
 			    int flags, int have_old)
 {
 	struct ref_update *update = add_update(transaction, refname);
diff --git a/refs.h b/refs.h
index 7d946f6..8c7f9c4 100644
--- a/refs.h
+++ b/refs.h
@@ -240,7 +240,8 @@ struct ref_transaction *ref_transaction_begin(void);
  */
 void ref_transaction_update(struct ref_transaction *transaction,
 			    const char *refname,
-			    unsigned char *new_sha1, unsigned char *old_sha1,
+			    const unsigned char *new_sha1,
+			    const unsigned char *old_sha1,
 			    int flags, int have_old);
 
 /*
@@ -251,7 +252,7 @@ void ref_transaction_update(struct ref_transaction *transaction,
  */
 void ref_transaction_create(struct ref_transaction *transaction,
 			    const char *refname,
-			    unsigned char *new_sha1,
+			    const unsigned char *new_sha1,
 			    int flags);
 
 /*
@@ -261,7 +262,7 @@ void ref_transaction_create(struct ref_transaction *transaction,
  */
 void ref_transaction_delete(struct ref_transaction *transaction,
 			    const char *refname,
-			    unsigned char *old_sha1,
+			    const unsigned char *old_sha1,
 			    int flags, int have_old);
 
 /*
-- 
2.0.1.546.gf603308

[PATCH v21 04/19] refs.c: allow passing NULL to ref_transaction_free

[Ronnie Sahlberg]

Allow ref_transaction_free(NULL) as a no-op. This makes ref_transaction_free
easier to use and more similar to plain 'free'.

In particular, it lets us rollback unconditionally as part of cleanup code
after setting 'transaction = NULL' if a transaction has been committed or
rolled back already.

Reviewed-by: Jonathan Nieder <jrnieder@gmail.com>
Reviewed-by: Michael Haggerty <mhagger@alum.mit.edu>
Signed-off-by: Ronnie Sahlberg <sahlberg@google.com>
---
 refs.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/refs.c b/refs.c
index 21ed465..1d6dece 100644
--- a/refs.c
+++ b/refs.c
@@ -3338,6 +3338,9 @@ void ref_transaction_free(struct ref_transaction *transaction)
 {
 	int i;
 
+	if (!transaction)
+		return;
+
 	for (i = 0; i < transaction->nr; i++)
 		free(transaction->updates[i]);
 
-- 
2.0.1.546.gf603308

[PATCH v21 05/19] refs.c: add a strbuf argument to ref_transaction_commit for error logging

[Ronnie Sahlberg]

Add a strbuf argument to _commit so that we can pass an error string back to
the caller. So that we can do error logging from the caller instead of from
_commit.

Longer term plan is to first convert all callers to use onerr==QUIET_ON_ERR
and craft any log messages from the callers themselves and finally remove the
onerr argument completely.

Reviewed-by: Jonathan Nieder <jrnieder@gmail.com>
Reviewed-by: Michael Haggerty <mhagger@alum.mit.edu>
Signed-off-by: Ronnie Sahlberg <sahlberg@google.com>
---
 builtin/update-ref.c | 2 +-
 refs.c               | 6 +++++-
 refs.h               | 5 ++++-
 3 files changed, 10 insertions(+), 3 deletions(-)

diff --git a/builtin/update-ref.c b/builtin/update-ref.c
index 1fd7a89..22617af 100644
--- a/builtin/update-ref.c
+++ b/builtin/update-ref.c
@@ -367,7 +367,7 @@ int cmd_update_ref(int argc, const char **argv, const char *prefix)
 		if (end_null)
 			line_termination = '\0';
 		update_refs_stdin();
-		ret = ref_transaction_commit(transaction, msg,
+		ret = ref_transaction_commit(transaction, msg, NULL,
 					     UPDATE_REFS_DIE_ON_ERR);
 		ref_transaction_free(transaction);
 		return ret;
diff --git a/refs.c b/refs.c
index 1d6dece..db05602 100644
--- a/refs.c
+++ b/refs.c
@@ -3444,7 +3444,8 @@ static int ref_update_reject_duplicates(struct ref_update **updates, int n,
 }
 
 int ref_transaction_commit(struct ref_transaction *transaction,
-			   const char *msg, enum action_on_err onerr)
+			   const char *msg, struct strbuf *err,
+			   enum action_on_err onerr)
 {
 	int ret = 0, delnum = 0, i;
 	const char **delnames;
@@ -3473,6 +3474,9 @@ int ref_transaction_commit(struct ref_transaction *transaction,
 					       update->flags,
 					       &update->type, onerr);
 		if (!update->lock) {
+			if (err)
+				strbuf_addf(err, "Cannot lock the ref '%s'.",
+					    update->refname);
 			ret = 1;
 			goto cleanup;
 		}
diff --git a/refs.h b/refs.h
index 8c7f9c4..09d3564 100644
--- a/refs.h
+++ b/refs.h
@@ -269,9 +269,12 @@ void ref_transaction_delete(struct ref_transaction *transaction,
  * Commit all of the changes that have been queued in transaction, as
  * atomically as possible.  Return a nonzero value if there is a
  * problem.
+ * If err is non-NULL we will add an error string to it to explain why
+ * the transaction failed. The string does not end in newline.
  */
 int ref_transaction_commit(struct ref_transaction *transaction,
-			   const char *msg, enum action_on_err onerr);
+			   const char *msg, struct strbuf *err,
+			   enum action_on_err onerr);
 
 /*
  * Free an existing transaction and all associated data.
-- 
2.0.1.546.gf603308

[PATCH v21 06/19] lockfile.c: add a new public function unable_to_lock_message

[Ronnie Sahlberg]

Introducing a new unable_to_lock_message helper, which has nicer
semantics than unable_to_lock_error and cleans up lockfile.c a little.

Signed-off-by: Ronnie Sahlberg <sahlberg@google.com>
Reviewed-by: Michael Haggerty <mhagger@alum.mit.edu>
---
 cache.h    |  2 ++
 lockfile.c | 22 ++++++++++++----------
 2 files changed, 14 insertions(+), 10 deletions(-)

diff --git a/cache.h b/cache.h
index df65231..8a46294 100644
--- a/cache.h
+++ b/cache.h
@@ -559,6 +559,8 @@ struct lock_file {
 #define LOCK_DIE_ON_ERROR 1
 #define LOCK_NODEREF 2
 extern int unable_to_lock_error(const char *path, int err);
+extern void unable_to_lock_message(const char *path, int err,
+				   struct strbuf *buf);
 extern NORETURN void unable_to_lock_index_die(const char *path, int err);
 extern int hold_lock_file_for_update(struct lock_file *, const char *path, int);
 extern int hold_lock_file_for_append(struct lock_file *, const char *path, int);
diff --git a/lockfile.c b/lockfile.c
index 8fbcb6a..464031b 100644
--- a/lockfile.c
+++ b/lockfile.c
@@ -157,33 +157,35 @@ static int lock_file(struct lock_file *lk, const char *path, int flags)
 	return lk->fd;
 }
 
-static char *unable_to_lock_message(const char *path, int err)
+void unable_to_lock_message(const char *path, int err, struct strbuf *buf)
 {
-	struct strbuf buf = STRBUF_INIT;
-
 	if (err == EEXIST) {
-		strbuf_addf(&buf, "Unable to create '%s.lock': %s.\n\n"
+		strbuf_addf(buf, "Unable to create '%s.lock': %s.\n\n"
 		    "If no other git process is currently running, this probably means a\n"
 		    "git process crashed in this repository earlier. Make sure no other git\n"
 		    "process is running and remove the file manually to continue.",
 			    absolute_path(path), strerror(err));
 	} else
-		strbuf_addf(&buf, "Unable to create '%s.lock': %s",
+		strbuf_addf(buf, "Unable to create '%s.lock': %s",
 			    absolute_path(path), strerror(err));
-	return strbuf_detach(&buf, NULL);
 }
 
 int unable_to_lock_error(const char *path, int err)
 {
-	char *msg = unable_to_lock_message(path, err);
-	error("%s", msg);
-	free(msg);
+	struct strbuf buf = STRBUF_INIT;
+
+	unable_to_lock_message(path, err, &buf);
+	error("%s", buf.buf);
+	strbuf_release(&buf);
 	return -1;
 }
 
 NORETURN void unable_to_lock_index_die(const char *path, int err)
 {
-	die("%s", unable_to_lock_message(path, err));
+	struct strbuf buf = STRBUF_INIT;
+
+	unable_to_lock_message(path, err, &buf);
+	die("%s", buf.buf);
 }
 
 int hold_lock_file_for_update(struct lock_file *lk, const char *path, int flags)
-- 
2.0.1.546.gf603308

[PATCH v21 07/19] lockfile.c: make lock_file return a meaningful errno on failure

[Ronnie Sahlberg]

Making errno when returning from lock_file() meaningful, which should
fix

 * an existing almost-bug in lock_ref_sha1_basic where it assumes
   errno==ENOENT is meaningful and could waste some work on retries

 * an existing bug in repack_without_refs where it prints
   strerror(errno) and picks advice based on errno, despite errno
   potentially being zero and potentially having been clobbered by
   that point

Signed-off-by: Ronnie Sahlberg <sahlberg@google.com>
Reviewed-by: Michael Haggerty <mhagger@alum.mit.edu>
---
 lockfile.c | 17 ++++++++++++-----
 refs.c     |  1 +
 refs.h     |  1 +
 3 files changed, 14 insertions(+), 5 deletions(-)

diff --git a/lockfile.c b/lockfile.c
index 464031b..a921d77 100644
--- a/lockfile.c
+++ b/lockfile.c
@@ -121,7 +121,7 @@ static char *resolve_symlink(char *p, size_t s)
 	return p;
 }
 
-
+/* Make sure errno contains a meaningful value on error */
 static int lock_file(struct lock_file *lk, const char *path, int flags)
 {
 	/*
@@ -130,8 +130,10 @@ static int lock_file(struct lock_file *lk, const char *path, int flags)
 	 */
 	static const size_t max_path_len = sizeof(lk->filename) - 5;
 
-	if (strlen(path) >= max_path_len)
+	if (strlen(path) >= max_path_len) {
+		errno = ENAMETOOLONG;
 		return -1;
+	}
 	strcpy(lk->filename, path);
 	if (!(flags & LOCK_NODEREF))
 		resolve_symlink(lk->filename, max_path_len);
@@ -148,9 +150,13 @@ static int lock_file(struct lock_file *lk, const char *path, int flags)
 			lock_file_list = lk;
 			lk->on_list = 1;
 		}
-		if (adjust_shared_perm(lk->filename))
-			return error("cannot fix permission bits on %s",
-				     lk->filename);
+		if (adjust_shared_perm(lk->filename)) {
+			int save_errno = errno;
+			error("cannot fix permission bits on %s",
+			      lk->filename);
+			errno = save_errno;
+			return -1;
+		}
 	}
 	else
 		lk->filename[0] = 0;
@@ -188,6 +194,7 @@ NORETURN void unable_to_lock_index_die(const char *path, int err)
 	die("%s", buf.buf);
 }
 
+/* This should return a meaningful errno on failure */
 int hold_lock_file_for_update(struct lock_file *lk, const char *path, int flags)
 {
 	int fd = lock_file(lk, path, flags);
diff --git a/refs.c b/refs.c
index db05602..e9d53e4 100644
--- a/refs.c
+++ b/refs.c
@@ -2212,6 +2212,7 @@ static int write_packed_entry_fn(struct ref_entry *entry, void *cb_data)
 	return 0;
 }
 
+/* This should return a meaningful errno on failure */
 int lock_packed_refs(int flags)
 {
 	struct packed_ref_cache *packed_ref_cache;
diff --git a/refs.h b/refs.h
index 09d3564..64f25d9 100644
--- a/refs.h
+++ b/refs.h
@@ -82,6 +82,7 @@ extern void warn_dangling_symrefs(FILE *fp, const char *msg_fmt, const struct st
 /*
  * Lock the packed-refs file for writing.  Flags is passed to
  * hold_lock_file_for_update().  Return 0 on success.
+ * Errno is set to something meaningful on error.
  */
 extern int lock_packed_refs(int flags);
 
-- 
2.0.1.546.gf603308

[PATCH v21 08/19] refs.c: add an err argument to repack_without_refs

[Ronnie Sahlberg]

Update repack_without_refs to take an err argument and update it if there
is a failure. Pass the err variable from ref_transaction_commit to this
function so that callers can print a meaningful error message if _commit
fails due to this function.

Signed-off-by: Ronnie Sahlberg <sahlberg@google.com>
Reviewed-by: Michael Haggerty <mhagger@alum.mit.edu>
---
 builtin/remote.c |  5 +++--
 refs.c           | 19 ++++++++++++++-----
 refs.h           |  3 ++-
 3 files changed, 19 insertions(+), 8 deletions(-)

diff --git a/builtin/remote.c b/builtin/remote.c
index c9102e8..401feb3 100644
--- a/builtin/remote.c
+++ b/builtin/remote.c
@@ -755,7 +755,7 @@ static int remove_branches(struct string_list *branches)
 	branch_names = xmalloc(branches->nr * sizeof(*branch_names));
 	for (i = 0; i < branches->nr; i++)
 		branch_names[i] = branches->items[i].string;
-	result |= repack_without_refs(branch_names, branches->nr);
+	result |= repack_without_refs(branch_names, branches->nr, NULL);
 	free(branch_names);
 
 	for (i = 0; i < branches->nr; i++) {
@@ -1333,7 +1333,8 @@ static int prune_remote(const char *remote, int dry_run)
 		for (i = 0; i < states.stale.nr; i++)
 			delete_refs[i] = states.stale.items[i].util;
 		if (!dry_run)
-			result |= repack_without_refs(delete_refs, states.stale.nr);
+			result |= repack_without_refs(delete_refs,
+						      states.stale.nr, NULL);
 		free(delete_refs);
 	}
 
diff --git a/refs.c b/refs.c
index e9d53e4..67a0217 100644
--- a/refs.c
+++ b/refs.c
@@ -2456,12 +2456,12 @@ static int curate_packed_ref_fn(struct ref_entry *entry, void *cb_data)
 	return 0;
 }
 
-int repack_without_refs(const char **refnames, int n)
+int repack_without_refs(const char **refnames, int n, struct strbuf *err)
 {
 	struct ref_dir *packed;
 	struct string_list refs_to_delete = STRING_LIST_INIT_DUP;
 	struct string_list_item *ref_to_delete;
-	int i, removed = 0;
+	int i, ret, removed = 0;
 
 	/* Look for a packed ref */
 	for (i = 0; i < n; i++)
@@ -2473,6 +2473,11 @@ int repack_without_refs(const char **refnames, int n)
 		return 0; /* no refname exists in packed refs */
 
 	if (lock_packed_refs(0)) {
+		if (err) {
+			unable_to_lock_message(git_path("packed-refs"), errno,
+					       err);
+			return -1;
+		}
 		unable_to_lock_error(git_path("packed-refs"), errno);
 		return error("cannot delete '%s' from packed refs", refnames[i]);
 	}
@@ -2499,12 +2504,16 @@ int repack_without_refs(const char **refnames, int n)
 	}
 
 	/* Write what remains */
-	return commit_packed_refs();
+	ret = commit_packed_refs();
+	if (ret && err)
+		strbuf_addf(err, "unable to overwrite old ref-pack file: %s",
+			    strerror(errno));
+	return ret;
 }
 
 static int repack_without_ref(const char *refname)
 {
-	return repack_without_refs(&refname, 1);
+	return repack_without_refs(&refname, 1, NULL);
 }
 
 static int delete_ref_loose(struct ref_lock *lock, int flag)
@@ -3508,7 +3517,7 @@ int ref_transaction_commit(struct ref_transaction *transaction,
 		}
 	}
 
-	ret |= repack_without_refs(delnames, delnum);
+	ret |= repack_without_refs(delnames, delnum, err);
 	for (i = 0; i < delnum; i++)
 		unlink_or_warn(git_path("logs/%s", delnames[i]));
 	clear_loose_ref_cache(&ref_cache);
diff --git a/refs.h b/refs.h
index 64f25d9..65f7637 100644
--- a/refs.h
+++ b/refs.h
@@ -122,7 +122,8 @@ extern void rollback_packed_refs(void);
  */
 int pack_refs(unsigned int flags);
 
-extern int repack_without_refs(const char **refnames, int n);
+extern int repack_without_refs(const char **refnames, int n,
+			       struct strbuf *err);
 
 extern int ref_exists(const char *);
 
-- 
2.0.1.546.gf603308

[PATCH v21 09/19] refs.c: make sure log_ref_setup returns a meaningful errno

[Ronnie Sahlberg]

Making errno when returning from log_ref_setup() meaningful,

Signed-off-by: Ronnie Sahlberg <sahlberg@google.com>
Reviewed-by: Michael Haggerty <mhagger@alum.mit.edu>
---
 refs.c | 27 +++++++++++++++++++--------
 refs.h |  4 +++-
 2 files changed, 22 insertions(+), 9 deletions(-)

diff --git a/refs.c b/refs.c
index 67a0217..9ea519c 100644
--- a/refs.c
+++ b/refs.c
@@ -2751,6 +2751,7 @@ static int copy_msg(char *buf, const char *msg)
 	return cp - buf;
 }
 
+/* This function must set a meaningful errno on failure */
 int log_ref_setup(const char *refname, char *logfile, int bufsize)
 {
 	int logfd, oflags = O_APPEND | O_WRONLY;
@@ -2761,9 +2762,12 @@ int log_ref_setup(const char *refname, char *logfile, int bufsize)
 	     starts_with(refname, "refs/remotes/") ||
 	     starts_with(refname, "refs/notes/") ||
 	     !strcmp(refname, "HEAD"))) {
-		if (safe_create_leading_directories(logfile) < 0)
-			return error("unable to create directory for %s",
-				     logfile);
+		if (safe_create_leading_directories(logfile) < 0) {
+			int save_errno = errno;
+			error("unable to create directory for %s", logfile);
+			errno = save_errno;
+			return -1;
+		}
 		oflags |= O_CREAT;
 	}
 
@@ -2774,15 +2778,22 @@ int log_ref_setup(const char *refname, char *logfile, int bufsize)
 
 		if ((oflags & O_CREAT) && errno == EISDIR) {
 			if (remove_empty_directories(logfile)) {
-				return error("There are still logs under '%s'",
-					     logfile);
+				int save_errno = errno;
+				error("There are still logs under '%s'",
+				      logfile);
+				errno = save_errno;
+				return -1;
 			}
 			logfd = open(logfile, oflags, 0666);
 		}
 
-		if (logfd < 0)
-			return error("Unable to append to %s: %s",
-				     logfile, strerror(errno));
+		if (logfd < 0) {
+			int save_errno = errno;
+			error("Unable to append to %s: %s", logfile,
+			      strerror(errno));
+			errno = save_errno;
+			return -1;
+		}
 	}
 
 	adjust_shared_perm(logfile);
diff --git a/refs.h b/refs.h
index 65f7637..82cc5cb 100644
--- a/refs.h
+++ b/refs.h
@@ -158,7 +158,9 @@ extern void unlock_ref(struct ref_lock *lock);
 /** Writes sha1 into the ref specified by the lock. **/
 extern int write_ref_sha1(struct ref_lock *lock, const unsigned char *sha1, const char *msg);
 
-/** Setup reflog before using. **/
+/*
+ * Setup reflog before using. Set errno to something meaningful on failure.
+ */
 int log_ref_setup(const char *refname, char *logfile, int bufsize);
 
 /** Reads log for the value of ref during at_time. **/
-- 
2.0.1.546.gf603308

[PATCH v21 10/19] refs.c: verify_lock should set errno to something meaningful

[Ronnie Sahlberg]

Making errno when returning from verify_lock() meaningful, which
should almost but not completely fix

 * a bug in "git fetch"'s s_update_ref, which trusts the result of an
   errno == ENOTDIR check to detect D/F conflicts

ENOTDIR makes sense as a sign that a file was in the way of a
directory we wanted to create.  Should "git fetch" also look for
ENOTEMPTY or EEXIST to catch cases where a directory was in the way
of a file to be created?

Signed-off-by: Ronnie Sahlberg <sahlberg@google.com>
Reviewed-by: Michael Haggerty <mhagger@alum.mit.edu>
---
 refs.c | 4 ++++
 refs.h | 6 +++++-
 2 files changed, 9 insertions(+), 1 deletion(-)

diff --git a/refs.c b/refs.c
index 9ea519c..a48f805 100644
--- a/refs.c
+++ b/refs.c
@@ -1932,18 +1932,22 @@ int refname_match(const char *abbrev_name, const char *full_name)
 	return 0;
 }
 
+/* This function should make sure errno is meaningful on error */
 static struct ref_lock *verify_lock(struct ref_lock *lock,
 	const unsigned char *old_sha1, int mustexist)
 {
 	if (read_ref_full(lock->ref_name, lock->old_sha1, mustexist, NULL)) {
+		int save_errno = errno;
 		error("Can't verify ref %s", lock->ref_name);
 		unlock_ref(lock);
+		errno = save_errno;
 		return NULL;
 	}
 	if (hashcmp(lock->old_sha1, old_sha1)) {
 		error("Ref %s is at %s but expected %s", lock->ref_name,
 			sha1_to_hex(lock->old_sha1), sha1_to_hex(old_sha1));
 		unlock_ref(lock);
+		errno = EBUSY;
 		return NULL;
 	}
 	return lock;
diff --git a/refs.h b/refs.h
index 82cc5cb..8d6cac7 100644
--- a/refs.h
+++ b/refs.h
@@ -137,11 +137,15 @@ extern int ref_exists(const char *);
  */
 extern int peel_ref(const char *refname, unsigned char *sha1);
 
-/** Locks a "refs/" ref returning the lock on success and NULL on failure. **/
+/*
+ * Locks a "refs/" ref returning the lock on success and NULL on failure.
+ * On failure errno is set to something meaningful.
+ */
 extern struct ref_lock *lock_ref_sha1(const char *refname, const unsigned char *old_sha1);
 
 /** Locks any ref (for 'HEAD' type refs). */
 #define REF_NODEREF	0x01
+/* errno is set to something meaningful on failure */
 extern struct ref_lock *lock_any_ref_for_update(const char *refname,
 						const unsigned char *old_sha1,
 						int flags, int *type_p);
-- 
2.0.1.546.gf603308

[PATCH v21 11/19] refs.c: make remove_empty_directories always set errno to something sane

[Ronnie Sahlberg]

Making errno when returning from remove_empty_directories() more
obviously meaningful, which should provide some peace of mind for
people auditing lock_ref_sha1_basic.

Signed-off-by: Ronnie Sahlberg <sahlberg@google.com>
Reviewed-by: Michael Haggerty <mhagger@alum.mit.edu>
---
 refs.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/refs.c b/refs.c
index a48f805..cc69581 100644
--- a/refs.c
+++ b/refs.c
@@ -1960,14 +1960,16 @@ static int remove_empty_directories(const char *file)
 	 * only empty directories), remove them.
 	 */
 	struct strbuf path;
-	int result;
+	int result, save_errno;
 
 	strbuf_init(&path, 20);
 	strbuf_addstr(&path, file);
 
 	result = remove_dir_recursively(&path, REMOVE_DIR_EMPTY_ONLY);
+	save_errno = errno;
 
 	strbuf_release(&path);
+	errno = save_errno;
 
 	return result;
 }
@@ -2056,6 +2058,7 @@ int dwim_log(const char *str, int len, unsigned char *sha1, char **log)
 	return logs_found;
 }
 
+/* This function should make sure errno is meaningful on error */
 static struct ref_lock *lock_ref_sha1_basic(const char *refname,
 					    const unsigned char *old_sha1,
 					    int flags, int *type_p)
-- 
2.0.1.546.gf603308

[PATCH v21 12/19] refs.c: commit_packed_refs to return a meaningful errno on failure

[Ronnie Sahlberg]

Making errno when returning from commit_packed_refs() meaningful,
which should fix

 * a bug in "git clone" where it prints strerror(errno) based on
   errno, despite errno possibly being zero and potentially having
   been clobbered by that point
 * the same kind of bug in "git pack-refs"

and prepares for repack_without_refs() to get a meaningful
error message when commit_packed_refs() fails without falling into
the same bug.

Signed-off-by: Ronnie Sahlberg <sahlberg@google.com>
Reviewed-by: Michael Haggerty <mhagger@alum.mit.edu>
---
 refs.c | 10 +++++++++-
 refs.h |  1 +
 2 files changed, 10 insertions(+), 1 deletion(-)

diff --git a/refs.c b/refs.c
index cc69581..7a815be 100644
--- a/refs.c
+++ b/refs.c
@@ -2239,11 +2239,16 @@ int lock_packed_refs(int flags)
 	return 0;
 }
 
+/*
+ * Commit the packed refs changes.
+ * On error we must make sure that errno contains a meaningful value.
+ */
 int commit_packed_refs(void)
 {
 	struct packed_ref_cache *packed_ref_cache =
 		get_packed_ref_cache(&ref_cache);
 	int error = 0;
+	int save_errno = 0;
 
 	if (!packed_ref_cache->lock)
 		die("internal error: packed-refs not locked");
@@ -2253,10 +2258,13 @@ int commit_packed_refs(void)
 	do_for_each_entry_in_dir(get_packed_ref_dir(packed_ref_cache),
 				 0, write_packed_entry_fn,
 				 &packed_ref_cache->lock->fd);
-	if (commit_lock_file(packed_ref_cache->lock))
+	if (commit_lock_file(packed_ref_cache->lock)) {
+		save_errno = errno;
 		error = -1;
+	}
 	packed_ref_cache->lock = NULL;
 	release_packed_ref_cache(packed_ref_cache);
+	errno = save_errno;
 	return error;
 }
 
diff --git a/refs.h b/refs.h
index 8d6cac7..e588ff8 100644
--- a/refs.h
+++ b/refs.h
@@ -98,6 +98,7 @@ extern void add_packed_ref(const char *refname, const unsigned char *sha1);
  * Write the current version of the packed refs cache from memory to
  * disk.  The packed-refs file must already be locked for writing (see
  * lock_packed_refs()).  Return zero on success.
+ * Sets errno to something meaningful on error.
  */
 extern int commit_packed_refs(void);
 
-- 
2.0.1.546.gf603308

[PATCH v21 13/19] refs.c: make resolve_ref_unsafe set errno to something meaningful on error

[Ronnie Sahlberg]

Making errno when returning from resolve_ref_unsafe() meaningful,
which should fix

 * a bug in lock_ref_sha1_basic, where it assumes EISDIR
   means it failed due to a directory being in the way

Signed-off-by: Ronnie Sahlberg <sahlberg@google.com>
Reviewed-by: Michael Haggerty <mhagger@alum.mit.edu>
---
 cache.h |  2 +-
 refs.c  | 19 +++++++++++++++----
 2 files changed, 16 insertions(+), 5 deletions(-)

diff --git a/cache.h b/cache.h
index 8a46294..4ca4583 100644
--- a/cache.h
+++ b/cache.h
@@ -979,7 +979,7 @@ extern int read_ref(const char *refname, unsigned char *sha1);
  * NULL.  If more than MAXDEPTH recursive symbolic lookups are needed,
  * give up and return NULL.
  *
- * errno is sometimes set on errors, but not always.
+ * errno is set to something meaningful on error.
  */
 extern const char *resolve_ref_unsafe(const char *ref, unsigned char *sha1, int reading, int *flag);
 extern char *resolve_refdup(const char *ref, unsigned char *sha1, int reading, int *flag);
diff --git a/refs.c b/refs.c
index 7a815be..211429d 100644
--- a/refs.c
+++ b/refs.c
@@ -1334,6 +1334,7 @@ static const char *handle_missing_loose_ref(const char *refname,
 	}
 }
 
+/* This function needs to return a meaningful errno on failure */
 const char *resolve_ref_unsafe(const char *refname, unsigned char *sha1, int reading, int *flag)
 {
 	int depth = MAXDEPTH;
@@ -1344,8 +1345,10 @@ const char *resolve_ref_unsafe(const char *refname, unsigned char *sha1, int rea
 	if (flag)
 		*flag = 0;
 
-	if (check_refname_format(refname, REFNAME_ALLOW_ONELEVEL))
+	if (check_refname_format(refname, REFNAME_ALLOW_ONELEVEL)) {
+		errno = EINVAL;
 		return NULL;
+	}
 
 	for (;;) {
 		char path[PATH_MAX];
@@ -1353,8 +1356,10 @@ const char *resolve_ref_unsafe(const char *refname, unsigned char *sha1, int rea
 		char *buf;
 		int fd;
 
-		if (--depth < 0)
+		if (--depth < 0) {
+			errno = ELOOP;
 			return NULL;
+		}
 
 		git_snpath(path, sizeof(path), "%s", refname);
 
@@ -1416,9 +1421,13 @@ const char *resolve_ref_unsafe(const char *refname, unsigned char *sha1, int rea
 				return NULL;
 		}
 		len = read_in_full(fd, buffer, sizeof(buffer)-1);
-		close(fd);
-		if (len < 0)
+		if (len < 0) {
+			int save_errno = errno;
+			close(fd);
+			errno = save_errno;
 			return NULL;
+		}
+		close(fd);
 		while (len && isspace(buffer[len-1]))
 			len--;
 		buffer[len] = '\0';
@@ -1435,6 +1444,7 @@ const char *resolve_ref_unsafe(const char *refname, unsigned char *sha1, int rea
 			    (buffer[40] != '\0' && !isspace(buffer[40]))) {
 				if (flag)
 					*flag |= REF_ISBROKEN;
+				errno = EINVAL;
 				return NULL;
 			}
 			return refname;
@@ -1447,6 +1457,7 @@ const char *resolve_ref_unsafe(const char *refname, unsigned char *sha1, int rea
 		if (check_refname_format(buf, REFNAME_ALLOW_ONELEVEL)) {
 			if (flag)
 				*flag |= REF_ISBROKEN;
+			errno = EINVAL;
 			return NULL;
 		}
 		refname = strcpy(refname_buffer, buf);
-- 
2.0.1.546.gf603308

[PATCH v21 14/19] refs.c: log_ref_write should try to return meaningful errno

[Ronnie Sahlberg]

Making errno from write_ref_sha1() meaningful, which should fix

* a bug in "git checkout -b" where it prints strerror(errno)
  despite errno possibly being zero or clobbered

* a bug in "git fetch"'s s_update_ref, which trusts the result of an
  errno == ENOTDIR check to detect D/F conflicts

Signed-off-by: Ronnie Sahlberg <sahlberg@google.com>
Reviewed-by: Michael Haggerty <mhagger@alum.mit.edu>
---
 refs.c | 28 +++++++++++++++++++++++-----
 1 file changed, 23 insertions(+), 5 deletions(-)

diff --git a/refs.c b/refs.c
index 211429d..61570c9 100644
--- a/refs.c
+++ b/refs.c
@@ -2859,8 +2859,19 @@ static int log_ref_write(const char *refname, const unsigned char *old_sha1,
 		len += copy_msg(logrec + len - 1, msg) - 1;
 	written = len <= maxlen ? write_in_full(logfd, logrec, len) : -1;
 	free(logrec);
-	if (close(logfd) != 0 || written != len)
-		return error("Unable to append to %s", log_file);
+	if (written != len) {
+		int save_errno = errno;
+		close(logfd);
+		error("Unable to append to %s", log_file);
+		errno = save_errno;
+		return -1;
+	}
+	if (close(logfd)) {
+		int save_errno = errno;
+		error("Unable to append to %s", log_file);
+		errno = save_errno;
+		return -1;
+	}
 	return 0;
 }
 
@@ -2869,14 +2880,17 @@ static int is_branch(const char *refname)
 	return !strcmp(refname, "HEAD") || starts_with(refname, "refs/heads/");
 }
 
+/* This function must return a meaningful errno */
 int write_ref_sha1(struct ref_lock *lock,
 	const unsigned char *sha1, const char *logmsg)
 {
 	static char term = '\n';
 	struct object *o;
 
-	if (!lock)
+	if (!lock) {
+		errno = EINVAL;
 		return -1;
+	}
 	if (!lock->force_write && !hashcmp(lock->old_sha1, sha1)) {
 		unlock_ref(lock);
 		return 0;
@@ -2886,19 +2900,23 @@ int write_ref_sha1(struct ref_lock *lock,
 		error("Trying to write ref %s with nonexistent object %s",
 			lock->ref_name, sha1_to_hex(sha1));
 		unlock_ref(lock);
+		errno = EINVAL;
 		return -1;
 	}
 	if (o->type != OBJ_COMMIT && is_branch(lock->ref_name)) {
 		error("Trying to write non-commit object %s to branch %s",
 			sha1_to_hex(sha1), lock->ref_name);
 		unlock_ref(lock);
+		errno = EINVAL;
 		return -1;
 	}
 	if (write_in_full(lock->lock_fd, sha1_to_hex(sha1), 40) != 40 ||
-	    write_in_full(lock->lock_fd, &term, 1) != 1
-		|| close_ref(lock) < 0) {
+	    write_in_full(lock->lock_fd, &term, 1) != 1 ||
+	    close_ref(lock) < 0) {
+		int save_errno = errno;
 		error("Couldn't write %s", lock->lk->filename);
 		unlock_ref(lock);
+		errno = save_errno;
 		return -1;
 	}
 	clear_loose_ref_cache(&ref_cache);
-- 
2.0.1.546.gf603308

[PATCH v21 15/19] refs.c: make ref_update_reject_duplicates take a strbuf argument for errors

[Ronnie Sahlberg]

Make ref_update_reject_duplicates return any error that occurs through a
new strbuf argument. This means that when a transaction commit fails in
this function we will now be able to pass a helpful error message back to the
caller.

Reviewed-by: Jonathan Nieder <jrnieder@gmail.com>
Reviewed-by: Michael Haggerty <mhagger@alum.mit.edu>
Signed-off-by: Ronnie Sahlberg <sahlberg@google.com>
---
 refs.c | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/refs.c b/refs.c
index 61570c9..115f143 100644
--- a/refs.c
+++ b/refs.c
@@ -3488,6 +3488,7 @@ static int ref_update_compare(const void *r1, const void *r2)
 }
 
 static int ref_update_reject_duplicates(struct ref_update **updates, int n,
+					struct strbuf *err,
 					enum action_on_err onerr)
 {
 	int i;
@@ -3495,6 +3496,9 @@ static int ref_update_reject_duplicates(struct ref_update **updates, int n,
 		if (!strcmp(updates[i - 1]->refname, updates[i]->refname)) {
 			const char *str =
 				"Multiple updates for ref '%s' not allowed.";
+			if (err)
+				strbuf_addf(err, str, updates[i]->refname);
+
 			switch (onerr) {
 			case UPDATE_REFS_MSG_ON_ERR:
 				error(str, updates[i]->refname); break;
@@ -3525,7 +3529,7 @@ int ref_transaction_commit(struct ref_transaction *transaction,
 
 	/* Copy, sort, and reject duplicate refs */
 	qsort(updates, n, sizeof(*updates), ref_update_compare);
-	ret = ref_update_reject_duplicates(updates, n, onerr);
+	ret = ref_update_reject_duplicates(updates, n, err, onerr);
 	if (ret)
 		goto cleanup;
 
-- 
2.0.1.546.gf603308

[PATCH v21 16/19] refs.c: make update_ref_write update a strbuf on failure

[Ronnie Sahlberg]

Change update_ref_write to also update an error strbuf on failure.
This makes the error available to ref_transaction_commit callers if the
transaction failed due to update_ref_sha1/write_ref_sha1 failures.

Reviewed-by: Jonathan Nieder <jrnieder@gmail.com>
Reviewed-by: Michael Haggerty <mhagger@alum.mit.edu>
Signed-off-by: Ronnie Sahlberg <sahlberg@google.com>
---
 refs.c | 9 ++++++---
 1 file changed, 6 insertions(+), 3 deletions(-)

diff --git a/refs.c b/refs.c
index 115f143..003b313 100644
--- a/refs.c
+++ b/refs.c
@@ -3353,10 +3353,13 @@ static struct ref_lock *update_ref_lock(const char *refname,
 
 static int update_ref_write(const char *action, const char *refname,
 			    const unsigned char *sha1, struct ref_lock *lock,
-			    enum action_on_err onerr)
+			    struct strbuf *err, enum action_on_err onerr)
 {
 	if (write_ref_sha1(lock, sha1, action) < 0) {
 		const char *str = "Cannot update the ref '%s'.";
+		if (err)
+			strbuf_addf(err, str, refname);
+
 		switch (onerr) {
 		case UPDATE_REFS_MSG_ON_ERR: error(str, refname); break;
 		case UPDATE_REFS_DIE_ON_ERR: die(str, refname); break;
@@ -3477,7 +3480,7 @@ int update_ref(const char *action, const char *refname,
 	lock = update_ref_lock(refname, oldval, flags, NULL, onerr);
 	if (!lock)
 		return 1;
-	return update_ref_write(action, refname, sha1, lock, onerr);
+	return update_ref_write(action, refname, sha1, lock, NULL, onerr);
 }
 
 static int ref_update_compare(const void *r1, const void *r2)
@@ -3559,7 +3562,7 @@ int ref_transaction_commit(struct ref_transaction *transaction,
 			ret = update_ref_write(msg,
 					       update->refname,
 					       update->new_sha1,
-					       update->lock, onerr);
+					       update->lock, err, onerr);
 			update->lock = NULL; /* freed by update_ref_write */
 			if (ret)
 				goto cleanup;
-- 
2.0.1.546.gf603308

[PATCH v21 17/19] update-ref: use err argument to get error from ref_transaction_commit

[Ronnie Sahlberg]

Call ref_transaction_commit with QUIET_ON_ERR and use the strbuf that is
returned to print a log message if/after the transaction fails.

Reviewed-by: Jonathan Nieder <jrnieder@gmail.com>
Reviewed-by: Michael Haggerty <mhagger@alum.mit.edu>
Signed-off-by: Ronnie Sahlberg <sahlberg@google.com>
---
 builtin/update-ref.c | 10 +++++-----
 1 file changed, 5 insertions(+), 5 deletions(-)

diff --git a/builtin/update-ref.c b/builtin/update-ref.c
index 22617af..aec9004 100644
--- a/builtin/update-ref.c
+++ b/builtin/update-ref.c
@@ -342,6 +342,7 @@ int cmd_update_ref(int argc, const char **argv, const char *prefix)
 	const char *refname, *oldval, *msg = NULL;
 	unsigned char sha1[20], oldsha1[20];
 	int delete = 0, no_deref = 0, read_stdin = 0, end_null = 0, flags = 0;
+	struct strbuf err = STRBUF_INIT;
 	struct option options[] = {
 		OPT_STRING( 'm', NULL, &msg, N_("reason"), N_("reason of the update")),
 		OPT_BOOL('d', NULL, &delete, N_("delete the reference")),
@@ -359,18 +360,17 @@ int cmd_update_ref(int argc, const char **argv, const char *prefix)
 		die("Refusing to perform update with empty message.");
 
 	if (read_stdin) {
-		int ret;
 		transaction = ref_transaction_begin();
-
 		if (delete || no_deref || argc > 0)
 			usage_with_options(git_update_ref_usage, options);
 		if (end_null)
 			line_termination = '\0';
 		update_refs_stdin();
-		ret = ref_transaction_commit(transaction, msg, NULL,
-					     UPDATE_REFS_DIE_ON_ERR);
+		if (ref_transaction_commit(transaction, msg, &err,
+					   UPDATE_REFS_QUIET_ON_ERR))
+			die("%s", err.buf);
 		ref_transaction_free(transaction);
-		return ret;
+		return 0;
 	}
 
 	if (end_null)
-- 
2.0.1.546.gf603308

[PATCH v21 18/19] refs.c: remove the onerr argument to ref_transaction_commit

[Ronnie Sahlberg]

Since all callers now use QUIET_ON_ERR we no longer need to provide an onerr
argument any more. Remove the onerr argument from the ref_transaction_commit
signature.

Reviewed-by: Jonathan Nieder <jrnieder@gmail.com>
Reviewed-by: Michael Haggerty <mhagger@alum.mit.edu>
Signed-off-by: Ronnie Sahlberg <sahlberg@google.com>
---
 builtin/update-ref.c |  3 +--
 refs.c               | 22 +++++++---------------
 refs.h               |  3 +--
 3 files changed, 9 insertions(+), 19 deletions(-)

diff --git a/builtin/update-ref.c b/builtin/update-ref.c
index aec9004..88ab785 100644
--- a/builtin/update-ref.c
+++ b/builtin/update-ref.c
@@ -366,8 +366,7 @@ int cmd_update_ref(int argc, const char **argv, const char *prefix)
 		if (end_null)
 			line_termination = '\0';
 		update_refs_stdin();
-		if (ref_transaction_commit(transaction, msg, &err,
-					   UPDATE_REFS_QUIET_ON_ERR))
+		if (ref_transaction_commit(transaction, msg, &err))
 			die("%s", err.buf);
 		ref_transaction_free(transaction);
 		return 0;
diff --git a/refs.c b/refs.c
index 003b313..4f78bd9 100644
--- a/refs.c
+++ b/refs.c
@@ -3491,8 +3491,7 @@ static int ref_update_compare(const void *r1, const void *r2)
 }
 
 static int ref_update_reject_duplicates(struct ref_update **updates, int n,
-					struct strbuf *err,
-					enum action_on_err onerr)
+					struct strbuf *err)
 {
 	int i;
 	for (i = 1; i < n; i++)
@@ -3502,22 +3501,13 @@ static int ref_update_reject_duplicates(struct ref_update **updates, int n,
 			if (err)
 				strbuf_addf(err, str, updates[i]->refname);
 
-			switch (onerr) {
-			case UPDATE_REFS_MSG_ON_ERR:
-				error(str, updates[i]->refname); break;
-			case UPDATE_REFS_DIE_ON_ERR:
-				die(str, updates[i]->refname); break;
-			case UPDATE_REFS_QUIET_ON_ERR:
-				break;
-			}
 			return 1;
 		}
 	return 0;
 }
 
 int ref_transaction_commit(struct ref_transaction *transaction,
-			   const char *msg, struct strbuf *err,
-			   enum action_on_err onerr)
+			   const char *msg, struct strbuf *err)
 {
 	int ret = 0, delnum = 0, i;
 	const char **delnames;
@@ -3532,7 +3522,7 @@ int ref_transaction_commit(struct ref_transaction *transaction,
 
 	/* Copy, sort, and reject duplicate refs */
 	qsort(updates, n, sizeof(*updates), ref_update_compare);
-	ret = ref_update_reject_duplicates(updates, n, err, onerr);
+	ret = ref_update_reject_duplicates(updates, n, err);
 	if (ret)
 		goto cleanup;
 
@@ -3544,7 +3534,8 @@ int ref_transaction_commit(struct ref_transaction *transaction,
 					       (update->have_old ?
 						update->old_sha1 : NULL),
 					       update->flags,
-					       &update->type, onerr);
+					       &update->type,
+					       UPDATE_REFS_QUIET_ON_ERR);
 		if (!update->lock) {
 			if (err)
 				strbuf_addf(err, "Cannot lock the ref '%s'.",
@@ -3562,7 +3553,8 @@ int ref_transaction_commit(struct ref_transaction *transaction,
 			ret = update_ref_write(msg,
 					       update->refname,
 					       update->new_sha1,
-					       update->lock, err, onerr);
+					       update->lock, err,
+					       UPDATE_REFS_QUIET_ON_ERR);
 			update->lock = NULL; /* freed by update_ref_write */
 			if (ret)
 				goto cleanup;
diff --git a/refs.h b/refs.h
index e588ff8..163b45c 100644
--- a/refs.h
+++ b/refs.h
@@ -282,8 +282,7 @@ void ref_transaction_delete(struct ref_transaction *transaction,
  * the transaction failed. The string does not end in newline.
  */
 int ref_transaction_commit(struct ref_transaction *transaction,
-			   const char *msg, struct strbuf *err,
-			   enum action_on_err onerr);
+			   const char *msg, struct strbuf *err);
 
 /*
  * Free an existing transaction and all associated data.
-- 
2.0.1.546.gf603308

[PATCH v21 19/19] refs.c: change ref_transaction_update() to do error checking and return status

[Ronnie Sahlberg]

Update ref_transaction_update() do some basic error checking and return
non-zero on error. Update all callers to check ref_transaction_update() for
error. There are currently no conditions in _update that will return error but
there will be in the future. Add an err argument that will be updated on
failure. In future patches we will start doing both locking and checking
for name conflicts in _update instead of _commit at which time this function
will start returning errors for these conditions.

Also check for BUGs during update and die(BUG:...) if we are calling
_update with have_old but the old_sha1 pointer is NULL.

Reviewed-by: Jonathan Nieder <jrnieder@gmail.com>
Reviewed-by: Michael Haggerty <mhagger@alum.mit.edu>
Signed-off-by: Ronnie Sahlberg <sahlberg@google.com>
---
 builtin/update-ref.c | 12 +++++++-----
 refs.c               | 18 ++++++++++++------
 refs.h               | 14 +++++++++-----
 3 files changed, 28 insertions(+), 16 deletions(-)

diff --git a/builtin/update-ref.c b/builtin/update-ref.c
index 88ab785..3067b11 100644
--- a/builtin/update-ref.c
+++ b/builtin/update-ref.c
@@ -16,6 +16,7 @@ static struct ref_transaction *transaction;
 
 static char line_termination = '\n';
 static int update_flags;
+static struct strbuf err = STRBUF_INIT;
 
 /*
  * Parse one whitespace- or NUL-terminated, possibly C-quoted argument
@@ -197,8 +198,9 @@ static const char *parse_cmd_update(struct strbuf *input, const char *next)
 	if (*next != line_termination)
 		die("update %s: extra input: %s", refname, next);
 
-	ref_transaction_update(transaction, refname, new_sha1, old_sha1,
-			       update_flags, have_old);
+	if (ref_transaction_update(transaction, refname, new_sha1, old_sha1,
+				   update_flags, have_old, &err))
+		die("%s", err.buf);
 
 	update_flags = 0;
 	free(refname);
@@ -286,8 +288,9 @@ static const char *parse_cmd_verify(struct strbuf *input, const char *next)
 	if (*next != line_termination)
 		die("verify %s: extra input: %s", refname, next);
 
-	ref_transaction_update(transaction, refname, new_sha1, old_sha1,
-			       update_flags, have_old);
+	if (ref_transaction_update(transaction, refname, new_sha1, old_sha1,
+				   update_flags, have_old, &err))
+		die("%s", err.buf);
 
 	update_flags = 0;
 	free(refname);
@@ -342,7 +345,6 @@ int cmd_update_ref(int argc, const char **argv, const char *prefix)
 	const char *refname, *oldval, *msg = NULL;
 	unsigned char sha1[20], oldsha1[20];
 	int delete = 0, no_deref = 0, read_stdin = 0, end_null = 0, flags = 0;
-	struct strbuf err = STRBUF_INIT;
 	struct option options[] = {
 		OPT_STRING( 'm', NULL, &msg, N_("reason"), N_("reason of the update")),
 		OPT_BOOL('d', NULL, &delete, N_("delete the reference")),
diff --git a/refs.c b/refs.c
index 4f78bd9..3f05e88 100644
--- a/refs.c
+++ b/refs.c
@@ -3428,19 +3428,25 @@ static struct ref_update *add_update(struct ref_transaction *transaction,
 	return update;
 }
 
-void ref_transaction_update(struct ref_transaction *transaction,
-			    const char *refname,
-			    const unsigned char *new_sha1,
-			    const unsigned char *old_sha1,
-			    int flags, int have_old)
+int ref_transaction_update(struct ref_transaction *transaction,
+			   const char *refname,
+			   const unsigned char *new_sha1,
+			   const unsigned char *old_sha1,
+			   int flags, int have_old,
+			   struct strbuf *err)
 {
-	struct ref_update *update = add_update(transaction, refname);
+	struct ref_update *update;
+
+	if (have_old && !old_sha1)
+		die("BUG: have_old is true but old_sha1 is NULL");
 
+	update = add_update(transaction, refname);
 	hashcpy(update->new_sha1, new_sha1);
 	update->flags = flags;
 	update->have_old = have_old;
 	if (have_old)
 		hashcpy(update->old_sha1, old_sha1);
+	return 0;
 }
 
 void ref_transaction_create(struct ref_transaction *transaction,
diff --git a/refs.h b/refs.h
index 163b45c..c5376ce 100644
--- a/refs.h
+++ b/refs.h
@@ -246,12 +246,16 @@ struct ref_transaction *ref_transaction_begin(void);
  * be deleted.  If have_old is true, then old_sha1 holds the value
  * that the reference should have had before the update, or zeros if
  * it must not have existed beforehand.
+ * Function returns 0 on success and non-zero on failure. A failure to update
+ * means that the transaction as a whole has failed and will need to be
+ * rolled back. On failure the err buffer will be updated.
  */
-void ref_transaction_update(struct ref_transaction *transaction,
-			    const char *refname,
-			    const unsigned char *new_sha1,
-			    const unsigned char *old_sha1,
-			    int flags, int have_old);
+int ref_transaction_update(struct ref_transaction *transaction,
+			   const char *refname,
+			   const unsigned char *new_sha1,
+			   const unsigned char *old_sha1,
+			   int flags, int have_old,
+			   struct strbuf *err);
 
 /*
  * Add a reference creation to transaction.  new_sha1 is the value
-- 
2.0.1.546.gf603308