[PATCH v8 0/7] ref backend preamble

[PATCH v8 0/7] ref backend preamble

[David Turner]

The current state of the discussion on alternate ref backends is that
we're going to continue to store pseudorefs (e.g. CHERRY_PICK_HEAD) as
files in $GIT_DIR.  So this re-roll of the refs backend preamble
doesn't do anything to pseudorefs.  It just does reflog stuff.

In addition, this version removes the over-aggressive die() on reflog
update failure from v7.  It adds the REF_FORCE_CREATE_REFLOG flag, as
Michael Haggerty suggested.  And it fixes commit message or two, as
suggested.  I believe this addresses all comments I've seen on v7.

This addresses Johannes Sixt's concerns too, by removing the offending
code.

[PATCH v8 1/7] refs.c: add err arguments to reflog functions

[David Turner]

Add an err argument to log_ref_setup that can explain the reason
for a failure. This then eliminates the need to manage errno through
this function since we can just add strerror(errno) to the err string
when meaningful. No callers relied on errno from this function for
anything else than the error message.

Also add err arguments to private functions write_ref_to_lockfile,
log_ref_write_1, commit_ref_update. This again eliminates the need to
manage errno in these functions.

Some error messages are slightly reordered.

Update of a patch by Ronnie Sahlberg.

Signed-off-by: Ronnie Sahlberg <sahlberg@google.com>
Signed-off-by: David Turner <dturner@twopensource.com>
---
 builtin/checkout.c |   8 ++--
 refs.c             | 127 +++++++++++++++++++++++++++++++----------------------
 refs.h             |   4 +-
 3 files changed, 81 insertions(+), 58 deletions(-)

diff --git a/builtin/checkout.c b/builtin/checkout.c
index c018ab3..93f63d3 100644
--- a/builtin/checkout.c
+++ b/builtin/checkout.c
@@ -624,16 +624,18 @@ static void update_refs_for_switch(const struct checkout_opts *opts,
 				struct strbuf log_file = STRBUF_INIT;
 				int ret;
 				const char *ref_name;
+				struct strbuf err = STRBUF_INIT;
 
 				ref_name = mkpath("refs/heads/%s", opts->new_orphan_branch);
 				temp = log_all_ref_updates;
 				log_all_ref_updates = 1;
-				ret = log_ref_setup(ref_name, &log_file);
+				ret = log_ref_setup(ref_name, &log_file, &err);
 				log_all_ref_updates = temp;
 				strbuf_release(&log_file);
 				if (ret) {
-					fprintf(stderr, _("Can not do reflog for '%s'\n"),
-					    opts->new_orphan_branch);
+					fprintf(stderr, _("Can not do reflog for '%s'. %s\n"),
+						opts->new_orphan_branch, err.buf);
+					strbuf_release(&err);
 					return;
 				}
 			}
diff --git a/refs.c b/refs.c
index fb568d7..03e7505 100644
--- a/refs.c
+++ b/refs.c
@@ -2975,9 +2975,11 @@ static int rename_ref_available(const char *oldname, const char *newname)
 	return ret;
 }
 
-static int write_ref_to_lockfile(struct ref_lock *lock, const unsigned char *sha1);
+static int write_ref_to_lockfile(struct ref_lock *lock,
+				 const unsigned char *sha1, struct strbuf *err);
 static int commit_ref_update(struct ref_lock *lock,
-			     const unsigned char *sha1, const char *logmsg);
+			     const unsigned char *sha1, const char *logmsg,
+			     struct strbuf *err);
 
 int rename_ref(const char *oldrefname, const char *newrefname, const char *logmsg)
 {
@@ -3038,9 +3040,10 @@ int rename_ref(const char *oldrefname, const char *newrefname, const char *logms
 	}
 	hashcpy(lock->old_oid.hash, orig_sha1);
 
-	if (write_ref_to_lockfile(lock, orig_sha1) ||
-	    commit_ref_update(lock, orig_sha1, logmsg)) {
-		error("unable to write current sha1 into %s", newrefname);
+	if (write_ref_to_lockfile(lock, orig_sha1, &err) ||
+	    commit_ref_update(lock, orig_sha1, logmsg, &err)) {
+		error("unable to write current sha1 into %s: %s", newrefname, err.buf);
+		strbuf_release(&err);
 		goto rollback;
 	}
 
@@ -3056,9 +3059,11 @@ int rename_ref(const char *oldrefname, const char *newrefname, const char *logms
 
 	flag = log_all_ref_updates;
 	log_all_ref_updates = 0;
-	if (write_ref_to_lockfile(lock, orig_sha1) ||
-	    commit_ref_update(lock, orig_sha1, NULL))
-		error("unable to write current sha1 into %s", oldrefname);
+	if (write_ref_to_lockfile(lock, orig_sha1, &err) ||
+	    commit_ref_update(lock, orig_sha1, NULL, &err)) {
+		error("unable to write current sha1 into %s: %s", oldrefname, err.buf);
+		strbuf_release(&err);
+	}
 	log_all_ref_updates = flag;
 
  rollbacklog:
@@ -3113,8 +3118,8 @@ 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, struct strbuf *sb_logfile)
+/* This function will fill in *err and return -1 on failure */
+int log_ref_setup(const char *refname, struct strbuf *sb_logfile, struct strbuf *err)
 {
 	int logfd, oflags = O_APPEND | O_WRONLY;
 	char *logfile;
@@ -3129,9 +3134,8 @@ int log_ref_setup(const char *refname, struct strbuf *sb_logfile)
 	     starts_with(refname, "refs/notes/") ||
 	     !strcmp(refname, "HEAD"))) {
 		if (safe_create_leading_directories(logfile) < 0) {
-			int save_errno = errno;
-			error("unable to create directory for %s", logfile);
-			errno = save_errno;
+			strbuf_addf(err, "unable to create directory for %s. "
+				    "%s", logfile, strerror(errno));
 			return -1;
 		}
 		oflags |= O_CREAT;
@@ -3144,20 +3148,16 @@ int log_ref_setup(const char *refname, struct strbuf *sb_logfile)
 
 		if (errno == EISDIR) {
 			if (remove_empty_directories(logfile)) {
-				int save_errno = errno;
-				error("There are still logs under '%s'",
-				      logfile);
-				errno = save_errno;
+				strbuf_addf(err, "There are still logs under "
+					    "'%s'", logfile);
 				return -1;
 			}
 			logfd = open(logfile, oflags, 0666);
 		}
 
 		if (logfd < 0) {
-			int save_errno = errno;
-			error("Unable to append to %s: %s", logfile,
-			      strerror(errno));
-			errno = save_errno;
+			strbuf_addf(err, "Unable to append to %s: %s",
+				    logfile, strerror(errno));
 			return -1;
 		}
 	}
@@ -3195,7 +3195,7 @@ static int log_ref_write_fd(int fd, const unsigned char *old_sha1,
 
 static int log_ref_write_1(const char *refname, const unsigned char *old_sha1,
 			   const unsigned char *new_sha1, const char *msg,
-			   struct strbuf *sb_log_file)
+			   struct strbuf *sb_log_file, struct strbuf *err)
 {
 	int logfd, result, oflags = O_APPEND | O_WRONLY;
 	char *log_file;
@@ -3203,7 +3203,8 @@ static int log_ref_write_1(const char *refname, const unsigned char *old_sha1,
 	if (log_all_ref_updates < 0)
 		log_all_ref_updates = !is_bare_repository();
 
-	result = log_ref_setup(refname, sb_log_file);
+	result = log_ref_setup(refname, sb_log_file, err);
+
 	if (result)
 		return result;
 	log_file = sb_log_file->buf;
@@ -3216,26 +3217,25 @@ static int log_ref_write_1(const char *refname, const unsigned char *old_sha1,
 	result = log_ref_write_fd(logfd, old_sha1, new_sha1,
 				  git_committer_info(0), msg);
 	if (result) {
-		int save_errno = errno;
+		strbuf_addf(err, "Unable to append to %s. %s", log_file,
+			    strerror(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;
+		strbuf_addf(err, "Unable to append to %s. %s", log_file,
+			    strerror(errno));
 		return -1;
 	}
 	return 0;
 }
 
 static int log_ref_write(const char *refname, const unsigned char *old_sha1,
-			 const unsigned char *new_sha1, const char *msg)
+			 const unsigned char *new_sha1, const char *msg,
+			 struct strbuf *err)
 {
 	struct strbuf sb = STRBUF_INIT;
-	int ret = log_ref_write_1(refname, old_sha1, new_sha1, msg, &sb);
+	int ret = log_ref_write_1(refname, old_sha1, new_sha1, msg, &sb, err);
 	strbuf_release(&sb);
 	return ret;
 }
@@ -3247,25 +3247,28 @@ int is_branch(const char *refname)
 
 /*
  * Write sha1 into the open lockfile, then close the lockfile. On
- * errors, rollback the lockfile and set errno to reflect the problem.
+ * errors, rollback the lockfile, fill in *err and
+ * return -1.
  */
 static int write_ref_to_lockfile(struct ref_lock *lock,
-				 const unsigned char *sha1)
+				 const unsigned char *sha1, struct strbuf *err)
 {
 	static char term = '\n';
 	struct object *o;
 
 	o = parse_object(sha1);
 	if (!o) {
-		error("Trying to write ref %s with nonexistent object %s",
-			lock->ref_name, sha1_to_hex(sha1));
+		strbuf_addf(err,
+			    "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);
+		strbuf_addf(err,
+			    "Trying to write non-commit object %s to branch %s",
+			    sha1_to_hex(sha1), lock->ref_name);
 		unlock_ref(lock);
 		errno = EINVAL;
 		return -1;
@@ -3273,10 +3276,9 @@ static int write_ref_to_lockfile(struct ref_lock *lock,
 	if (write_in_full(lock->lk->fd, sha1_to_hex(sha1), 40) != 40 ||
 	    write_in_full(lock->lk->fd, &term, 1) != 1 ||
 	    close_ref(lock) < 0) {
-		int save_errno = errno;
-		error("Couldn't write %s", lock->lk->filename.buf);
+		strbuf_addf(err,
+			    "Couldn't write %s", lock->lk->filename.buf);
 		unlock_ref(lock);
-		errno = save_errno;
 		return -1;
 	}
 	return 0;
@@ -3288,12 +3290,17 @@ static int write_ref_to_lockfile(struct ref_lock *lock,
  * necessary, using the specified lockmsg (which can be NULL).
  */
 static int commit_ref_update(struct ref_lock *lock,
-			     const unsigned char *sha1, const char *logmsg)
+			     const unsigned char *sha1, const char *logmsg,
+			     struct strbuf *err)
 {
 	clear_loose_ref_cache(&ref_cache);
-	if (log_ref_write(lock->ref_name, lock->old_oid.hash, sha1, logmsg) < 0 ||
+	if (log_ref_write(lock->ref_name, lock->old_oid.hash, sha1, logmsg, err) < 0 ||
 	    (strcmp(lock->ref_name, lock->orig_ref_name) &&
-	     log_ref_write(lock->orig_ref_name, lock->old_oid.hash, sha1, logmsg) < 0)) {
+	     log_ref_write(lock->orig_ref_name, lock->old_oid.hash, sha1, logmsg, err) < 0)) {
+		char *old_msg = strbuf_detach(err, NULL);
+		strbuf_addf(err, "Cannot update the ref '%s': '%s'",
+			    lock->ref_name, old_msg);
+		free(old_msg);
 		unlock_ref(lock);
 		return -1;
 	}
@@ -3316,14 +3323,21 @@ static int commit_ref_update(struct ref_lock *lock,
 		head_ref = resolve_ref_unsafe("HEAD", RESOLVE_REF_READING,
 					      head_sha1, &head_flag);
 		if (head_ref && (head_flag & REF_ISSYMREF) &&
-		    !strcmp(head_ref, lock->ref_name))
-			log_ref_write("HEAD", lock->old_oid.hash, sha1, logmsg);
+		    !strcmp(head_ref, lock->ref_name)) {
+			struct strbuf log_err = STRBUF_INIT;
+			if (log_ref_write("HEAD", lock->old_oid.hash, sha1,
+					  logmsg, &log_err)) {
+				error("%s", log_err.buf);
+				strbuf_release(&log_err);
+			}
+		}
 	}
 	if (commit_ref(lock)) {
 		error("Couldn't set %s", lock->ref_name);
 		unlock_ref(lock);
 		return -1;
 	}
+
 	unlock_ref(lock);
 	return 0;
 }
@@ -3336,6 +3350,7 @@ int create_symref(const char *ref_target, const char *refs_heads_master,
 	int fd, len, written;
 	char *git_HEAD = git_pathdup("%s", ref_target);
 	unsigned char old_sha1[20], new_sha1[20];
+	struct strbuf err = STRBUF_INIT;
 
 	if (logmsg && read_ref(ref_target, old_sha1))
 		hashclr(old_sha1);
@@ -3384,8 +3399,11 @@ int create_symref(const char *ref_target, const char *refs_heads_master,
 #ifndef NO_SYMLINK_HEAD
 	done:
 #endif
-	if (logmsg && !read_ref(refs_heads_master, new_sha1))
-		log_ref_write(ref_target, old_sha1, new_sha1, logmsg);
+	if (logmsg && !read_ref(refs_heads_master, new_sha1) &&
+		log_ref_write(ref_target, old_sha1, new_sha1, logmsg, &err)) {
+		error("%s", err.buf);
+		strbuf_release(&err);
+	}
 
 	free(git_HEAD);
 	return 0;
@@ -4021,14 +4039,19 @@ int ref_transaction_commit(struct ref_transaction *transaction,
 				 * value, so we don't need to write it.
 				 */
 			} else if (write_ref_to_lockfile(update->lock,
-							 update->new_sha1)) {
+							 update->new_sha1,
+							 err)) {
+				char *write_err = strbuf_detach(err, NULL);
+
 				/*
 				 * The lock was freed upon failure of
 				 * write_ref_to_lockfile():
 				 */
 				update->lock = NULL;
-				strbuf_addf(err, "cannot update the ref '%s'.",
-					    update->refname);
+				strbuf_addf(err,
+					    "cannot update the ref '%s': %s",
+					    update->refname, write_err);
+				free(write_err);
 				ret = TRANSACTION_GENERIC_ERROR;
 				goto cleanup;
 			} else {
@@ -4054,11 +4077,9 @@ int ref_transaction_commit(struct ref_transaction *transaction,
 
 		if (update->flags & REF_NEEDS_COMMIT) {
 			if (commit_ref_update(update->lock,
-					      update->new_sha1, update->msg)) {
+					      update->new_sha1, update->msg, err)) {
 				/* freed by commit_ref_update(): */
 				update->lock = NULL;
-				strbuf_addf(err, "Cannot update the ref '%s'.",
-					    update->refname);
 				ret = TRANSACTION_GENERIC_ERROR;
 				goto cleanup;
 			} else {
diff --git a/refs.h b/refs.h
index e82fca5..debdefc 100644
--- a/refs.h
+++ b/refs.h
@@ -226,9 +226,9 @@ int pack_refs(unsigned int flags);
 #define REF_NODEREF	0x01
 
 /*
- * Setup reflog before using. Set errno to something meaningful on failure.
+ * Setup reflog before using. Fill in err and return -1 on failure.
  */
-int log_ref_setup(const char *refname, struct strbuf *logfile);
+int log_ref_setup(const char *refname, struct strbuf *logfile, struct strbuf *err);
 
 /** Reads log for the value of ref during at_time. **/
 extern int read_ref_at(const char *refname, unsigned int flags,
-- 
2.0.5.499.g01f6352.dirty-twtrsrc

[PATCH v8 2/7] refs: Break out check for reflog autocreation

[David Turner]

This is just for clarity.

Signed-off-by: David Turner <dturner@twopensource.com>
---
 refs.c | 16 +++++++++++-----
 1 file changed, 11 insertions(+), 5 deletions(-)

diff --git a/refs.c b/refs.c
index 03e7505..903b401 100644
--- a/refs.c
+++ b/refs.c
@@ -3118,6 +3118,16 @@ static int copy_msg(char *buf, const char *msg)
 	return cp - buf;
 }
 
+static int should_autocreate_reflog(const char *refname)
+{
+	if (!log_all_ref_updates)
+		return 0;
+	return starts_with(refname, "refs/heads/") ||
+		starts_with(refname, "refs/remotes/") ||
+		starts_with(refname, "refs/notes/") ||
+		!strcmp(refname, "HEAD");
+}
+
 /* This function will fill in *err and return -1 on failure */
 int log_ref_setup(const char *refname, struct strbuf *sb_logfile, struct strbuf *err)
 {
@@ -3128,11 +3138,7 @@ int log_ref_setup(const char *refname, struct strbuf *sb_logfile, struct strbuf
 	logfile = sb_logfile->buf;
 	/* make sure the rest of the function can't change "logfile" */
 	sb_logfile = NULL;
-	if (log_all_ref_updates &&
-	    (starts_with(refname, "refs/heads/") ||
-	     starts_with(refname, "refs/remotes/") ||
-	     starts_with(refname, "refs/notes/") ||
-	     !strcmp(refname, "HEAD"))) {
+	if (should_autocreate_reflog(refname)) {
 		if (safe_create_leading_directories(logfile) < 0) {
 			strbuf_addf(err, "unable to create directory for %s. "
 				    "%s", logfile, strerror(errno));
-- 
2.0.5.499.g01f6352.dirty-twtrsrc

[PATCH v8 3/7] refs: new public ref function: safe_create_reflog

[David Turner]

The safe_create_reflog function creates a reflog, if it does not
already exist.

The log_ref_setup function becomes private and gains a force_create
parameter to force the creation of a reflog even if log_all_ref_updates
is false or the refname is not one of the special refnames.

The new parameter also reduces the need to store, modify, and restore
the log_all_ref_updates global before reflog creation.

In a moment, we will use this to add reflog creation commands to
git-reflog.

Signed-off-by: David Turner <dturner@twopensource.com>
---
 builtin/checkout.c | 16 ++++++----------
 refs.c             | 24 ++++++++++++++++++++----
 refs.h             |  2 +-
 3 files changed, 27 insertions(+), 15 deletions(-)

diff --git a/builtin/checkout.c b/builtin/checkout.c
index 93f63d3..9923fd5 100644
--- a/builtin/checkout.c
+++ b/builtin/checkout.c
@@ -620,24 +620,20 @@ static void update_refs_for_switch(const struct checkout_opts *opts,
 	if (opts->new_branch) {
 		if (opts->new_orphan_branch) {
 			if (opts->new_branch_log && !log_all_ref_updates) {
-				int temp;
-				struct strbuf log_file = STRBUF_INIT;
 				int ret;
-				const char *ref_name;
+				char *refname;
 				struct strbuf err = STRBUF_INIT;
 
-				ref_name = mkpath("refs/heads/%s", opts->new_orphan_branch);
-				temp = log_all_ref_updates;
-				log_all_ref_updates = 1;
-				ret = log_ref_setup(ref_name, &log_file, &err);
-				log_all_ref_updates = temp;
-				strbuf_release(&log_file);
+				refname = mkpathdup("refs/heads/%s", opts->new_orphan_branch);
+				ret = safe_create_reflog(refname, &err, 1);
+				free(refname);
 				if (ret) {
-					fprintf(stderr, _("Can not do reflog for '%s'. %s\n"),
+					fprintf(stderr, _("can not do reflog for '%s'. %s\n"),
 						opts->new_orphan_branch, err.buf);
 					strbuf_release(&err);
 					return;
 				}
+				strbuf_release(&err);
 			}
 		}
 		else
diff --git a/refs.c b/refs.c
index 903b401..4857f0b 100644
--- a/refs.c
+++ b/refs.c
@@ -3128,8 +3128,13 @@ static int should_autocreate_reflog(const char *refname)
 		!strcmp(refname, "HEAD");
 }
 
-/* This function will fill in *err and return -1 on failure */
-int log_ref_setup(const char *refname, struct strbuf *sb_logfile, struct strbuf *err)
+/*
+ * Create a reflog for a ref.  If force_create = 0, the reflog will
+ * only be created for certain refs (those for which
+ * should_autocreate_reflog returns non-zero.  Otherwise, create it
+ * regardless of the ref name.  Fill in *err and return -1 on failure.
+ */
+static int log_ref_setup(const char *refname, struct strbuf *sb_logfile, struct strbuf *err, int force_create)
 {
 	int logfd, oflags = O_APPEND | O_WRONLY;
 	char *logfile;
@@ -3138,7 +3143,7 @@ int log_ref_setup(const char *refname, struct strbuf *sb_logfile, struct strbuf
 	logfile = sb_logfile->buf;
 	/* make sure the rest of the function can't change "logfile" */
 	sb_logfile = NULL;
-	if (should_autocreate_reflog(refname)) {
+	if (force_create || should_autocreate_reflog(refname)) {
 		if (safe_create_leading_directories(logfile) < 0) {
 			strbuf_addf(err, "unable to create directory for %s. "
 				    "%s", logfile, strerror(errno));
@@ -3173,6 +3178,17 @@ int log_ref_setup(const char *refname, struct strbuf *sb_logfile, struct strbuf
 	return 0;
 }
 
+
+int safe_create_reflog(const char *refname, struct strbuf *err, int force_create)
+{
+	int ret;
+	struct strbuf sb = STRBUF_INIT;
+
+	ret = log_ref_setup(refname, &sb, err, force_create);
+	strbuf_release(&sb);
+	return ret;
+}
+
 static int log_ref_write_fd(int fd, const unsigned char *old_sha1,
 			    const unsigned char *new_sha1,
 			    const char *committer, const char *msg)
@@ -3209,7 +3225,7 @@ static int log_ref_write_1(const char *refname, const unsigned char *old_sha1,
 	if (log_all_ref_updates < 0)
 		log_all_ref_updates = !is_bare_repository();
 
-	result = log_ref_setup(refname, sb_log_file, err);
+	result = log_ref_setup(refname, sb_log_file, err, 0);
 
 	if (result)
 		return result;
diff --git a/refs.h b/refs.h
index debdefc..3b90e16 100644
--- a/refs.h
+++ b/refs.h
@@ -228,7 +228,7 @@ int pack_refs(unsigned int flags);
 /*
  * Setup reflog before using. Fill in err and return -1 on failure.
  */
-int log_ref_setup(const char *refname, struct strbuf *logfile, struct strbuf *err);
+int safe_create_reflog(const char *refname, struct strbuf *err, int force_create);
 
 /** Reads log for the value of ref during at_time. **/
 extern int read_ref_at(const char *refname, unsigned int flags,
-- 
2.0.5.499.g01f6352.dirty-twtrsrc

[PATCH v8 4/7] git-reflog: add exists command

[David Turner]

Theis are necessary because alternate ref backends might store reflogs
somewhere other than .git/logs.  Code that now directly manipulates
.git/logs should instead go through git-reflog.

Signed-off-by: David Turner <dturner@twopensource.com>
---
 Documentation/git-reflog.txt |  4 ++++
 builtin/reflog.c             | 33 ++++++++++++++++++++++++++++++++-
 t/t1411-reflog-show.sh       |  5 +++++
 3 files changed, 41 insertions(+), 1 deletion(-)

diff --git a/Documentation/git-reflog.txt b/Documentation/git-reflog.txt
index 5e7908e..4b08fc7 100644
--- a/Documentation/git-reflog.txt
+++ b/Documentation/git-reflog.txt
@@ -23,6 +23,7 @@ depending on the subcommand:
 	[--dry-run] [--verbose] [--all | <refs>...]
 'git reflog delete' [--rewrite] [--updateref]
 	[--dry-run] [--verbose] ref@\{specifier\}...
+'git reflog exists' <ref>
 
 Reference logs, or "reflogs", record when the tips of branches and
 other references were updated in the local repository. Reflogs are
@@ -52,6 +53,9 @@ argument must be an _exact_ entry (e.g. "`git reflog delete
 master@{2}`"). This subcommand is also typically not used directly by
 end users.
 
+The "exists" subcommand checks whether a ref has a reflog.  It exists
+with zero status if the reflog exists, and non-zero status if it does
+not.
 
 OPTIONS
 -------
diff --git a/builtin/reflog.c b/builtin/reflog.c
index c2eb8ff..7ed0e85 100644
--- a/builtin/reflog.c
+++ b/builtin/reflog.c
@@ -13,6 +13,8 @@ static const char reflog_expire_usage[] =
 "git reflog expire [--expire=<time>] [--expire-unreachable=<time>] [--rewrite] [--updateref] [--stale-fix] [--dry-run | -n] [--verbose] [--all] <refs>...";
 static const char reflog_delete_usage[] =
 "git reflog delete [--rewrite] [--updateref] [--dry-run | -n] [--verbose] <refs>...";
+static const char reflog_exists_usage[] =
+"git reflog exists <ref>";
 
 static unsigned long default_reflog_expire;
 static unsigned long default_reflog_expire_unreachable;
@@ -699,12 +701,38 @@ static int cmd_reflog_delete(int argc, const char **argv, const char *prefix)
 	return status;
 }
 
+static int cmd_reflog_exists(int argc, const char **argv, const char *prefix)
+{
+	int i, start = 0;
+
+	for (i = 1; i < argc; i++) {
+		const char *arg = argv[i];
+		if (!strcmp(arg, "--")) {
+			i++;
+			break;
+		}
+		else if (arg[0] == '-')
+			usage(reflog_exists_usage);
+		else
+			break;
+	}
+
+	start = i;
+
+	if (argc - start != 1)
+		usage(reflog_exists_usage);
+
+	if (check_refname_format(argv[start], REFNAME_ALLOW_ONELEVEL))
+		die("invalid ref format: %s", argv[start]);
+	return !reflog_exists(argv[start]);
+}
+
 /*
  * main "reflog"
  */
 
 static const char reflog_usage[] =
-"git reflog [ show | expire | delete ]";
+"git reflog [ show | expire | delete | exists ]";
 
 int cmd_reflog(int argc, const char **argv, const char *prefix)
 {
@@ -724,5 +752,8 @@ int cmd_reflog(int argc, const char **argv, const char *prefix)
 	if (!strcmp(argv[1], "delete"))
 		return cmd_reflog_delete(argc - 1, argv + 1, prefix);
 
+	if (!strcmp(argv[1], "exists"))
+		return cmd_reflog_exists(argc - 1, argv + 1, prefix);
+
 	return cmd_log_reflog(argc, argv, prefix);
 }
diff --git a/t/t1411-reflog-show.sh b/t/t1411-reflog-show.sh
index 6f47c0d..3eb4f10 100755
--- a/t/t1411-reflog-show.sh
+++ b/t/t1411-reflog-show.sh
@@ -166,4 +166,9 @@ test_expect_success 'git log -g -p shows diffs vs. parents' '
 	test_cmp expect actual
 '
 
+test_expect_success 'reflog exists works' '
+	git reflog exists refs/heads/master &&
+	! git reflog exists refs/heads/nonexistent
+'
+
 test_done
-- 
2.0.5.499.g01f6352.dirty-twtrsrc

[PATCH v8 5/7] refs: add REF_FORCE_CREATE_REFLOG flag

[David Turner]

Add a flag to allow forcing the creation of a reflog even if the ref
name and core.logAllRefUpdates setting would not ordinarily cause ref
creation.

In a moment, we will use this to add options to git tag and git
update-ref to force reflog creation.

Signed-off-by: David Turner <dturner@twopensource.com>
---
 refs.c | 34 +++++++++++++++++++++-------------
 refs.h |  1 +
 2 files changed, 22 insertions(+), 13 deletions(-)

diff --git a/refs.c b/refs.c
index 4857f0b..06c62c8 100644
--- a/refs.c
+++ b/refs.c
@@ -63,6 +63,11 @@ static unsigned char refname_disposition[256] = {
 #define REF_NEEDS_COMMIT 0x20
 
 /*
+ * 0x40 is REF_FORCE_CREATE_REFLOG, so skip it if you're adding a
+ * value to ref_update::flags
+ */
+
+/*
  * Try to read one refname component from the front of refname.
  * Return the length of the component found, or -1 if the component is
  * not legal.  It is legal if it is something reasonable to have under
@@ -2979,7 +2984,7 @@ static int write_ref_to_lockfile(struct ref_lock *lock,
 				 const unsigned char *sha1, struct strbuf *err);
 static int commit_ref_update(struct ref_lock *lock,
 			     const unsigned char *sha1, const char *logmsg,
-			     struct strbuf *err);
+			     int flags, struct strbuf *err);
 
 int rename_ref(const char *oldrefname, const char *newrefname, const char *logmsg)
 {
@@ -3041,7 +3046,7 @@ int rename_ref(const char *oldrefname, const char *newrefname, const char *logms
 	hashcpy(lock->old_oid.hash, orig_sha1);
 
 	if (write_ref_to_lockfile(lock, orig_sha1, &err) ||
-	    commit_ref_update(lock, orig_sha1, logmsg, &err)) {
+	    commit_ref_update(lock, orig_sha1, logmsg, 0, &err)) {
 		error("unable to write current sha1 into %s: %s", newrefname, err.buf);
 		strbuf_release(&err);
 		goto rollback;
@@ -3060,7 +3065,7 @@ int rename_ref(const char *oldrefname, const char *newrefname, const char *logms
 	flag = log_all_ref_updates;
 	log_all_ref_updates = 0;
 	if (write_ref_to_lockfile(lock, orig_sha1, &err) ||
-	    commit_ref_update(lock, orig_sha1, NULL, &err)) {
+	    commit_ref_update(lock, orig_sha1, NULL, 0, &err)) {
 		error("unable to write current sha1 into %s: %s", oldrefname, err.buf);
 		strbuf_release(&err);
 	}
@@ -3217,7 +3222,8 @@ static int log_ref_write_fd(int fd, const unsigned char *old_sha1,
 
 static int log_ref_write_1(const char *refname, const unsigned char *old_sha1,
 			   const unsigned char *new_sha1, const char *msg,
-			   struct strbuf *sb_log_file, struct strbuf *err)
+			   struct strbuf *sb_log_file, int flags,
+			   struct strbuf *err)
 {
 	int logfd, result, oflags = O_APPEND | O_WRONLY;
 	char *log_file;
@@ -3225,7 +3231,7 @@ static int log_ref_write_1(const char *refname, const unsigned char *old_sha1,
 	if (log_all_ref_updates < 0)
 		log_all_ref_updates = !is_bare_repository();
 
-	result = log_ref_setup(refname, sb_log_file, err, 0);
+	result = log_ref_setup(refname, sb_log_file, err, flags & REF_FORCE_CREATE_REFLOG);
 
 	if (result)
 		return result;
@@ -3254,10 +3260,11 @@ static int log_ref_write_1(const char *refname, const unsigned char *old_sha1,
 
 static int log_ref_write(const char *refname, const unsigned char *old_sha1,
 			 const unsigned char *new_sha1, const char *msg,
-			 struct strbuf *err)
+			 int flags, struct strbuf *err)
 {
 	struct strbuf sb = STRBUF_INIT;
-	int ret = log_ref_write_1(refname, old_sha1, new_sha1, msg, &sb, err);
+	int ret = log_ref_write_1(refname, old_sha1, new_sha1, msg, &sb, flags,
+				  err);
 	strbuf_release(&sb);
 	return ret;
 }
@@ -3313,12 +3320,12 @@ static int write_ref_to_lockfile(struct ref_lock *lock,
  */
 static int commit_ref_update(struct ref_lock *lock,
 			     const unsigned char *sha1, const char *logmsg,
-			     struct strbuf *err)
+			     int flags, struct strbuf *err)
 {
 	clear_loose_ref_cache(&ref_cache);
-	if (log_ref_write(lock->ref_name, lock->old_oid.hash, sha1, logmsg, err) < 0 ||
+	if (log_ref_write(lock->ref_name, lock->old_oid.hash, sha1, logmsg, flags, err) < 0 ||
 	    (strcmp(lock->ref_name, lock->orig_ref_name) &&
-	     log_ref_write(lock->orig_ref_name, lock->old_oid.hash, sha1, logmsg, err) < 0)) {
+	     log_ref_write(lock->orig_ref_name, lock->old_oid.hash, sha1, logmsg, flags, err) < 0)) {
 		char *old_msg = strbuf_detach(err, NULL);
 		strbuf_addf(err, "Cannot update the ref '%s': '%s'",
 			    lock->ref_name, old_msg);
@@ -3348,7 +3355,7 @@ static int commit_ref_update(struct ref_lock *lock,
 		    !strcmp(head_ref, lock->ref_name)) {
 			struct strbuf log_err = STRBUF_INIT;
 			if (log_ref_write("HEAD", lock->old_oid.hash, sha1,
-					  logmsg, &log_err)) {
+					  logmsg, 0, &log_err)) {
 				error("%s", log_err.buf);
 				strbuf_release(&log_err);
 			}
@@ -3422,7 +3429,7 @@ int create_symref(const char *ref_target, const char *refs_heads_master,
 	done:
 #endif
 	if (logmsg && !read_ref(refs_heads_master, new_sha1) &&
-		log_ref_write(ref_target, old_sha1, new_sha1, logmsg, &err)) {
+		log_ref_write(ref_target, old_sha1, new_sha1, logmsg, 0, &err)) {
 		error("%s", err.buf);
 		strbuf_release(&err);
 	}
@@ -4099,7 +4106,8 @@ int ref_transaction_commit(struct ref_transaction *transaction,
 
 		if (update->flags & REF_NEEDS_COMMIT) {
 			if (commit_ref_update(update->lock,
-					      update->new_sha1, update->msg, err)) {
+					      update->new_sha1, update->msg,
+					      update->flags, err)) {
 				/* freed by commit_ref_update(): */
 				update->lock = NULL;
 				ret = TRANSACTION_GENERIC_ERROR;
diff --git a/refs.h b/refs.h
index 3b90e16..297ec45 100644
--- a/refs.h
+++ b/refs.h
@@ -224,6 +224,7 @@ int pack_refs(unsigned int flags);
  * Other flags are reserved for internal use.
  */
 #define REF_NODEREF	0x01
+#define REF_FORCE_CREATE_REFLOG 0x40
 
 /*
  * Setup reflog before using. Fill in err and return -1 on failure.
-- 
2.0.5.499.g01f6352.dirty-twtrsrc

[PATCH v8 6/7] update-ref and tag: add --create-reflog arg

[David Turner]

Allow the creation of a ref (e.g. stash) with a reflog already in
place. For most refs (e.g. those under refs/heads), this happens
automatically, but for others, we need this option.

Currently, git does this by pre-creating the reflog, but alternate ref
backends might store reflogs somewhere other than .git/logs.  Code
that now directly manipulates .git/logs should instead use git
plumbing commands.

I also added --create-reflog to git tag, just for completeness.

In a moment, we will use this argument to make git stash work with
alternate ref backends.

Signed-off-by: David Turner <dturner@twopensource.com>
---
 Documentation/git-tag.txt        |  5 ++++-
 Documentation/git-update-ref.txt |  5 ++++-
 builtin/tag.c                    |  5 ++++-
 builtin/update-ref.c             | 14 +++++++++++---
 t/t1400-update-ref.sh            | 38 ++++++++++++++++++++++++++++++++++++++
 t/t7004-tag.sh                   | 14 +++++++++++++-
 6 files changed, 74 insertions(+), 7 deletions(-)

diff --git a/Documentation/git-tag.txt b/Documentation/git-tag.txt
index 034d10d..2312980 100644
--- a/Documentation/git-tag.txt
+++ b/Documentation/git-tag.txt
@@ -13,7 +13,7 @@ SYNOPSIS
 	<tagname> [<commit> | <object>]
 'git tag' -d <tagname>...
 'git tag' [-n[<num>]] -l [--contains <commit>] [--points-at <object>]
-	[--column[=<options>] | --no-column] [<pattern>...]
+	[--column[=<options>] | --no-column] [--create-reflog] [<pattern>...]
 	[<pattern>...]
 'git tag' -v <tagname>...
 
@@ -143,6 +143,9 @@ This option is only applicable when listing tags without annotation lines.
 	all, 'whitespace' removes just leading/trailing whitespace lines and
 	'strip' removes both whitespace and commentary.
 
+--create-reflog::
+	Create a reflog for the tag.
+
 <tagname>::
 	The name of the tag to create, delete, or describe.
 	The new tag name must pass all checks defined by
diff --git a/Documentation/git-update-ref.txt b/Documentation/git-update-ref.txt
index c8f5ae5..969bfab 100644
--- a/Documentation/git-update-ref.txt
+++ b/Documentation/git-update-ref.txt
@@ -8,7 +8,7 @@ git-update-ref - Update the object name stored in a ref safely
 SYNOPSIS
 --------
 [verse]
-'git update-ref' [-m <reason>] (-d <ref> [<oldvalue>] | [--no-deref] <ref> <newvalue> [<oldvalue>] | --stdin [-z])
+'git update-ref' [-m <reason>] (-d <ref> [<oldvalue>] | [--no-deref] [--create-reflog] <ref> <newvalue> [<oldvalue>] | --stdin [-z])
 
 DESCRIPTION
 -----------
@@ -67,6 +67,9 @@ performs all modifications together.  Specify commands of the form:
 	verify SP <ref> [SP <oldvalue>] LF
 	option SP <opt> LF
 
+With `--create-reflog`, update-ref will create a reflog for each ref
+even if one would not ordinarily be created.
+
 Quote fields containing whitespace as if they were strings in C source
 code; i.e., surrounded by double-quotes and with backslash escapes.
 Use 40 "0" characters or the empty string to specify a zero value.  To
diff --git a/builtin/tag.c b/builtin/tag.c
index 5f6cdc5..cccca99 100644
--- a/builtin/tag.c
+++ b/builtin/tag.c
@@ -579,6 +579,7 @@ int cmd_tag(int argc, const char **argv, const char *prefix)
 	struct create_tag_options opt;
 	char *cleanup_arg = NULL;
 	int annotate = 0, force = 0, lines = -1;
+	int create_reflog = 0;
 	int cmdmode = 0;
 	const char *msgfile = NULL, *keyid = NULL;
 	struct msg_arg msg = { 0, STRBUF_INIT };
@@ -605,6 +606,7 @@ int cmd_tag(int argc, const char **argv, const char *prefix)
 		OPT_STRING('u', "local-user", &keyid, N_("key-id"),
 					N_("use another key to sign the tag")),
 		OPT__FORCE(&force, N_("replace the tag if exists")),
+		OPT_BOOL(0, "create-reflog", &create_reflog, N_("create_reflog")),
 
 		OPT_GROUP(N_("Tag listing options")),
 		OPT_COLUMN(0, "column", &colopts, N_("show tag list in columns")),
@@ -733,7 +735,8 @@ int cmd_tag(int argc, const char **argv, const char *prefix)
 	transaction = ref_transaction_begin(&err);
 	if (!transaction ||
 	    ref_transaction_update(transaction, ref.buf, object, prev,
-				   0, NULL, &err) ||
+				   create_reflog ? REF_FORCE_CREATE_REFLOG : 0,
+				   NULL, &err) ||
 	    ref_transaction_commit(transaction, &err))
 		die("%s", err.buf);
 	ref_transaction_free(transaction);
diff --git a/builtin/update-ref.c b/builtin/update-ref.c
index 6763cf1..d9646ef 100644
--- a/builtin/update-ref.c
+++ b/builtin/update-ref.c
@@ -14,6 +14,7 @@ static const char * const git_update_ref_usage[] = {
 
 static char line_termination = '\n';
 static int update_flags;
+int create_reflog_flag;
 static const char *msg;
 
 /*
@@ -200,7 +201,8 @@ static const char *parse_cmd_update(struct ref_transaction *transaction,
 
 	if (ref_transaction_update(transaction, refname,
 				   new_sha1, have_old ? old_sha1 : NULL,
-				   update_flags, msg, &err))
+				   update_flags | create_reflog_flag,
+				   msg, &err))
 		die("%s", err.buf);
 
 	update_flags = 0;
@@ -231,7 +233,8 @@ static const char *parse_cmd_create(struct ref_transaction *transaction,
 		die("create %s: extra input: %s", refname, next);
 
 	if (ref_transaction_create(transaction, refname, new_sha1,
-				   update_flags, msg, &err))
+				   update_flags | create_reflog_flag,
+				   msg, &err))
 		die("%s", err.buf);
 
 	update_flags = 0;
@@ -354,6 +357,7 @@ int cmd_update_ref(int argc, const char **argv, const char *prefix)
 	unsigned char sha1[20], oldsha1[20];
 	int delete = 0, no_deref = 0, read_stdin = 0, end_null = 0;
 	unsigned int flags = 0;
+	int create_reflog = 0;
 	struct option options[] = {
 		OPT_STRING( 'm', NULL, &msg, N_("reason"), N_("reason of the update")),
 		OPT_BOOL('d', NULL, &delete, N_("delete the reference")),
@@ -361,6 +365,7 @@ int cmd_update_ref(int argc, const char **argv, const char *prefix)
 					N_("update <refname> not the one it points to")),
 		OPT_BOOL('z', NULL, &end_null, N_("stdin has NUL-terminated arguments")),
 		OPT_BOOL( 0 , "stdin", &read_stdin, N_("read updates from stdin")),
+		OPT_BOOL( 0 , "create-reflog", &create_reflog, N_("create_reflog")),
 		OPT_END(),
 	};
 
@@ -370,6 +375,8 @@ int cmd_update_ref(int argc, const char **argv, const char *prefix)
 	if (msg && !*msg)
 		die("Refusing to perform update with empty message.");
 
+	create_reflog_flag = create_reflog ? REF_FORCE_CREATE_REFLOG : 0;
+
 	if (read_stdin) {
 		struct strbuf err = STRBUF_INIT;
 		struct ref_transaction *transaction;
@@ -431,5 +438,6 @@ int cmd_update_ref(int argc, const char **argv, const char *prefix)
 				  flags);
 	else
 		return update_ref(msg, refname, sha1, oldval ? oldsha1 : NULL,
-				  flags, UPDATE_REFS_DIE_ON_ERR);
+				  flags | create_reflog_flag,
+				  UPDATE_REFS_DIE_ON_ERR);
 }
diff --git a/t/t1400-update-ref.sh b/t/t1400-update-ref.sh
index d787bf5..9d21c19 100755
--- a/t/t1400-update-ref.sh
+++ b/t/t1400-update-ref.sh
@@ -23,6 +23,7 @@ test_expect_success setup '
 m=refs/heads/master
 n_dir=refs/heads/gu
 n=$n_dir/fixes
+outside=foo
 
 test_expect_success \
 	"create $m" \
@@ -74,6 +75,24 @@ test_expect_success "delete $m (by HEAD)" '
 '
 rm -f .git/$m
 
+test_expect_success 'update-ref does not create reflogs by default' '
+	test_when_finished "git update-ref -d $outside" &&
+	git update-ref $outside $A &&
+	git rev-parse $A >expect &&
+	git rev-parse $outside >actual &&
+	test_cmp expect actual &&
+	test_must_fail git reflog exists $outside
+'
+
+test_expect_success 'update-ref creates reflogs with --create-reflog' '
+	test_when_finished "git update-ref -d $outside" &&
+	git update-ref --create-reflog $outside $A &&
+	git rev-parse $A >expect &&
+	git rev-parse $outside >actual &&
+	test_cmp expect actual &&
+	git reflog exists $outside
+'
+
 test_expect_success \
 	"create $m (by HEAD)" \
 	"git update-ref HEAD $A &&
@@ -472,6 +491,25 @@ test_expect_success 'stdin create ref works' '
 	test_cmp expect actual
 '
 
+test_expect_success 'stdin does not create reflogs by default' '
+	test_when_finished "git update-ref -d $outside" &&
+	echo "create $outside $m" >stdin &&
+	git update-ref --stdin <stdin &&
+	git rev-parse $m >expect &&
+	git rev-parse $outside >actual &&
+	test_cmp expect actual &&
+	test_must_fail git reflog exists $outside
+'
+
+test_expect_success 'stdin creates reflogs with --create-reflog' '
+	echo "create $outside $m" >stdin &&
+	git update-ref --create-reflog --stdin <stdin &&
+	git rev-parse $m >expect &&
+	git rev-parse $outside >actual &&
+	test_cmp expect actual &&
+	git reflog exists $outside
+'
+
 test_expect_success 'stdin succeeds with quoted argument' '
 	git update-ref -d $a &&
 	echo "create $a \"$m\"" >stdin &&
diff --git a/t/t7004-tag.sh b/t/t7004-tag.sh
index d1ff5c9..75423ab 100755
--- a/t/t7004-tag.sh
+++ b/t/t7004-tag.sh
@@ -51,7 +51,19 @@ test_expect_success 'creating a tag using default HEAD should succeed' '
 	echo foo >foo &&
 	git add foo &&
 	git commit -m Foo &&
-	git tag mytag
+	git tag mytag &&
+	test_must_fail git reflog exists refs/tags/mytag
+'
+
+test_expect_success 'creating a tag with --create-reflog should create reflog' '
+	test_when_finished "git tag -d tag_with_reflog" &&
+	git tag --create-reflog tag_with_reflog &&
+	git reflog exists refs/tags/tag_with_reflog
+'
+
+test_expect_success '--create-reflog does not creates reflog on failure' '
+	test_must_fail git tag --create-reflog mytag &&
+	test_must_fail git reflog exists refs/tags/tag_with_reflog
 '
 
 test_expect_success 'listing all tags if one exists should succeed' '
-- 
2.0.5.499.g01f6352.dirty-twtrsrc

[PATCH v8 7/7] git-stash: use update-ref --create-reflog instead of creating files

[David Turner]

This is in support of alternate ref backends which don't necessarily
store reflogs as files.

Signed-off-by: David Turner <dturner@twopensource.com>
---
 git-stash.sh | 6 ++----
 1 file changed, 2 insertions(+), 4 deletions(-)

diff --git a/git-stash.sh b/git-stash.sh
index 8e9e2cd..1d5ba7a 100755
--- a/git-stash.sh
+++ b/git-stash.sh
@@ -183,9 +183,7 @@ store_stash () {
 		stash_msg="Created via \"git stash store\"."
 	fi
 
-	# Make sure the reflog for stash is kept.
-	: >>"$(git rev-parse --git-path logs/$ref_stash)"
-	git update-ref -m "$stash_msg" $ref_stash $w_commit
+	git update-ref --create-reflog -m "$stash_msg" $ref_stash $w_commit
 	ret=$?
 	test $ret != 0 && test -z $quiet &&
 	die "$(eval_gettext "Cannot update \$ref_stash with \$w_commit")"
@@ -262,7 +260,7 @@ save_stash () {
 		say "$(gettext "No local changes to save")"
 		exit 0
 	fi
-	test -f "$(git rev-parse --git-path logs/$ref_stash)" ||
+	git reflog exists $ref_stash ||
 		clear_stash || die "$(gettext "Cannot initialize stash")"
 
 	create_stash "$stash_msg" $untracked
-- 
2.0.5.499.g01f6352.dirty-twtrsrc

Re: [PATCH v8 0/7] ref backend preamble

[Philip Oakley]

From: "David Turner" <dturner@twopensource.com>
> The current state of the discussion on alternate ref backends is that
> we're going to continue to store pseudorefs (e.g. CHERRY_PICK_HEAD) as

Assuming this is accepted, should the definition of pseudorefs be 
included in the gitglossary?

Once ref backends become common, the distinction will needed in the 
docs.

> files in $GIT_DIR.  So this re-roll of the refs backend preamble
> doesn't do anything to pseudorefs.  It just does reflog stuff.
>
--
Philip 

Re: [PATCH v8 0/7] ref backend preamble

[David Turner]

On Fri, 2015-07-10 at 15:34 +0100, Philip Oakley wrote:
> From: "David Turner" <dturner@twopensource.com>
> > The current state of the discussion on alternate ref backends is that
> > we're going to continue to store pseudorefs (e.g. CHERRY_PICK_HEAD) as
> 
> Assuming this is accepted, should the definition of pseudorefs be 
> included in the gitglossary?
>
> Once ref backends become common, the distinction will needed in the 
> docs.

This term is only in this message (that is, I don't think I used it in
any commit messages yet).  The code uses it in at least one place
already.  But yes, I think if we decided to go with the pseudoref
concept, we should document it.

Re: [PATCH v8 1/7] refs.c: add err arguments to reflog functions

[Michael Haggerty]

On 07/09/2015 03:50 PM, David Turner wrote:
> Add an err argument to log_ref_setup that can explain the reason
> for a failure. This then eliminates the need to manage errno through
> this function since we can just add strerror(errno) to the err string
> when meaningful. No callers relied on errno from this function for
> anything else than the error message.
> 
> Also add err arguments to private functions write_ref_to_lockfile,
> log_ref_write_1, commit_ref_update. This again eliminates the need to
> manage errno in these functions.
> 
> Some error messages are slightly reordered.
> 
> Update of a patch by Ronnie Sahlberg.
> 
> Signed-off-by: Ronnie Sahlberg <sahlberg@google.com>
> Signed-off-by: David Turner <dturner@twopensource.com>
> ---
>  builtin/checkout.c |   8 ++--
>  refs.c             | 127 +++++++++++++++++++++++++++++++----------------------
>  refs.h             |   4 +-
>  3 files changed, 81 insertions(+), 58 deletions(-)
> 
> diff --git a/builtin/checkout.c b/builtin/checkout.c
> index c018ab3..93f63d3 100644
> --- a/builtin/checkout.c
> +++ b/builtin/checkout.c
> @@ -624,16 +624,18 @@ static void update_refs_for_switch(const struct checkout_opts *opts,
>  				struct strbuf log_file = STRBUF_INIT;
>  				int ret;
>  				const char *ref_name;
> +				struct strbuf err = STRBUF_INIT;
>  
>  				ref_name = mkpath("refs/heads/%s", opts->new_orphan_branch);
>  				temp = log_all_ref_updates;
>  				log_all_ref_updates = 1;
> -				ret = log_ref_setup(ref_name, &log_file);
> +				ret = log_ref_setup(ref_name, &log_file, &err);
>  				log_all_ref_updates = temp;
>  				strbuf_release(&log_file);
>  				if (ret) {
> -					fprintf(stderr, _("Can not do reflog for '%s'\n"),
> -					    opts->new_orphan_branch);
> +					fprintf(stderr, _("Can not do reflog for '%s'. %s\n"),
> +						opts->new_orphan_branch, err.buf);

Our usual pattern for chaining error messages is

    $problem: $reason

In this patch (and maybe later patches too? I haven't checked yet) I see

    $problem. $reason

and also

    $problem. '$reason'

I think it would be good to use the first pattern consistently.

> +					strbuf_release(&err);
>  					return;
>  				}
>  			}
> diff --git a/refs.c b/refs.c
> index fb568d7..03e7505 100644
> --- a/refs.c
> +++ b/refs.c
> [...]
> @@ -3247,25 +3247,28 @@ int is_branch(const char *refname)
>  
>  /*
>   * Write sha1 into the open lockfile, then close the lockfile. On
> - * errors, rollback the lockfile and set errno to reflect the problem.
> + * errors, rollback the lockfile, fill in *err and
> + * return -1.
>   */
>  static int write_ref_to_lockfile(struct ref_lock *lock,
> -				 const unsigned char *sha1)
> +				 const unsigned char *sha1, struct strbuf *err)
>  {
>  	static char term = '\n';
>  	struct object *o;
>  
>  	o = parse_object(sha1);
>  	if (!o) {
> -		error("Trying to write ref %s with nonexistent object %s",
> -			lock->ref_name, sha1_to_hex(sha1));
> +		strbuf_addf(err,
> +			    "Trying to write ref %s with nonexistent object %s",
> +			    lock->ref_name, sha1_to_hex(sha1));
>  		unlock_ref(lock);
>  		errno = EINVAL;

Is it intentional that this function is still setting errno (here and a
few lines farther down)? I'm guessing that this is no longer needed,
though I haven't audited the callers.

>  		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);
> +		strbuf_addf(err,
> +			    "Trying to write non-commit object %s to branch %s",
> +			    sha1_to_hex(sha1), lock->ref_name);
>  		unlock_ref(lock);
>  		errno = EINVAL;
>  		return -1;
> [...]

Michael

-- 
Michael Haggerty
mhagger@alum.mit.edu

Re: [PATCH v8 4/7] git-reflog: add exists command

[Michael Haggerty]

On 07/09/2015 03:50 PM, David Turner wrote:
> Theis are necessary because alternate ref backends might store reflogs
> somewhere other than .git/logs.  Code that now directly manipulates
> .git/logs should instead go through git-reflog.
> 
> Signed-off-by: David Turner <dturner@twopensource.com>
> ---
>  Documentation/git-reflog.txt |  4 ++++
>  builtin/reflog.c             | 33 ++++++++++++++++++++++++++++++++-
>  t/t1411-reflog-show.sh       |  5 +++++
>  3 files changed, 41 insertions(+), 1 deletion(-)
> 
> diff --git a/Documentation/git-reflog.txt b/Documentation/git-reflog.txt
> index 5e7908e..4b08fc7 100644
> --- a/Documentation/git-reflog.txt
> +++ b/Documentation/git-reflog.txt
> @@ -23,6 +23,7 @@ depending on the subcommand:
>  	[--dry-run] [--verbose] [--all | <refs>...]
>  'git reflog delete' [--rewrite] [--updateref]
>  	[--dry-run] [--verbose] ref@\{specifier\}...
> +'git reflog exists' <ref>
>  
>  Reference logs, or "reflogs", record when the tips of branches and
>  other references were updated in the local repository. Reflogs are
> @@ -52,6 +53,9 @@ argument must be an _exact_ entry (e.g. "`git reflog delete
>  master@{2}`"). This subcommand is also typically not used directly by
>  end users.
>  
> +The "exists" subcommand checks whether a ref has a reflog.  It exists

The second "exists" should be "exits".

> +with zero status if the reflog exists, and non-zero status if it does
> +not.
>  
> [...]

Michael

-- 
Michael Haggerty
mhagger@alum.mit.edu

Re: [PATCH v8 6/7] update-ref and tag: add --create-reflog arg

[Michael Haggerty]

On 07/09/2015 03:50 PM, David Turner wrote:
> Allow the creation of a ref (e.g. stash) with a reflog already in
> place. For most refs (e.g. those under refs/heads), this happens
> automatically, but for others, we need this option.
> 
> Currently, git does this by pre-creating the reflog, but alternate ref
> backends might store reflogs somewhere other than .git/logs.  Code
> that now directly manipulates .git/logs should instead use git
> plumbing commands.
> 
> I also added --create-reflog to git tag, just for completeness.
> 
> In a moment, we will use this argument to make git stash work with
> alternate ref backends.
> 
> Signed-off-by: David Turner <dturner@twopensource.com>
> ---
>  Documentation/git-tag.txt        |  5 ++++-
>  Documentation/git-update-ref.txt |  5 ++++-
>  builtin/tag.c                    |  5 ++++-
>  builtin/update-ref.c             | 14 +++++++++++---
>  t/t1400-update-ref.sh            | 38 ++++++++++++++++++++++++++++++++++++++
>  t/t7004-tag.sh                   | 14 +++++++++++++-
>  6 files changed, 74 insertions(+), 7 deletions(-)
> 
> [...]
> diff --git a/t/t7004-tag.sh b/t/t7004-tag.sh
> index d1ff5c9..75423ab 100755
> --- a/t/t7004-tag.sh
> +++ b/t/t7004-tag.sh
> @@ -51,7 +51,19 @@ test_expect_success 'creating a tag using default HEAD should succeed' '
>  	echo foo >foo &&
>  	git add foo &&
>  	git commit -m Foo &&
> -	git tag mytag
> +	git tag mytag &&
> +	test_must_fail git reflog exists refs/tags/mytag
> +'
> +
> +test_expect_success 'creating a tag with --create-reflog should create reflog' '
> +	test_when_finished "git tag -d tag_with_reflog" &&
> +	git tag --create-reflog tag_with_reflog &&
> +	git reflog exists refs/tags/tag_with_reflog
> +'
> +
> +test_expect_success '--create-reflog does not creates reflog on failure' '

s/creates/create/

> +	test_must_fail git tag --create-reflog mytag &&
> +	test_must_fail git reflog exists refs/tags/tag_with_reflog

Shouldn't this be

	test_must_fail git reflog exists refs/tags/mytag

?

> [...]

Michael

-- 
Michael Haggerty
mhagger@alum.mit.edu

Re: [PATCH v8 0/7] ref backend preamble

[Michael Haggerty]

On 07/09/2015 03:50 PM, David Turner wrote:
> The current state of the discussion on alternate ref backends is that
> we're going to continue to store pseudorefs (e.g. CHERRY_PICK_HEAD) as
> files in $GIT_DIR.  So this re-roll of the refs backend preamble
> doesn't do anything to pseudorefs.  It just does reflog stuff.
> 
> In addition, this version removes the over-aggressive die() on reflog
> update failure from v7.  It adds the REF_FORCE_CREATE_REFLOG flag, as
> Michael Haggerty suggested.  And it fixes commit message or two, as
> suggested.  I believe this addresses all comments I've seen on v7.
> 
> This addresses Johannes Sixt's concerns too, by removing the offending
> code.

I just reviewed the whole patch series. Aside from the minor points that
I commented on, it all looks good to me.

Reviewed-by: Michael Haggerty <mhagger@alum.mit.edu>

Michael

-- 
Michael Haggerty
mhagger@alum.mit.edu