[PATCH v2] commit: run git gc --auto just before the pre-commit hook

["Ævar Arnfjörð Bjarmason" <avarab@gmail.com>]

Change the behavior of git-commit back to what it was back in
d4bb43ee27 ("Invoke "git gc --auto" from commit, merge, am and
rebase.", 2007-09-05) when it was git-commit.sh.

Shortly afterwards in f5bbc3225c ("Port git commit to C.", 2007-11-08)
when it was ported to C, the "git gc --auto" invocation went away.

Before this, git gc --auto only ran for
git-{am,merge,fetch,receive-pack}. Therefore it was possible to write
a script that would "git commit" a lot of data locally, and gc would
never run.

One such repository that was locally committing generated zone file
changes had grown to a size of ~60GB before a daily cronjob was added
to "git gc", bringing it down to less than 1GB. This will make such
cases work without intervention.

I think fixing such pathological cases where the repository will grow
forever is a worthwhile trade-off for spending a couple of
milliseconds calling "git gc --auto" (in the common cases where it
doesn't do anything).

Signed-off-by: Ævar Arnfjörð Bjarmason <avarab@gmail.com>
---

On Wed, Feb 28 2018, Junio C. Hamano jotted:

> Ævar Arnfjörð Bjarmason  <avarab@gmail.com> writes:
>
>> Change the behavior of git-commit back to what it was back in
>> d4bb43ee27 ("Invoke "git gc --auto" from commit, merge, am and
>> rebase.", 2007-09-05) when it was git-commit.sh.
>
> ... which was to run it just before post-commit.  Do I retitle this
> patch before queuing?

Do'h. Of course I screw up something simple like that, sorry. This v2
fixes it, and I also rephrased the commit message a bit (more commas &
full-stops).

> So this is a decade late regression fix?  As they say, better late
> than never, probably.

Yup.

I wonder if it would also be a good idea to run git gc --auto on "git
push". It itself won't create any objects, but it would be a nice
proxy in many cases for picking up anything else we missed due to
various object writing commands that won't run --auto.

 builtin/commit.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/builtin/commit.c b/builtin/commit.c
index e8e8d13be4..a16a056f6a 100644
--- a/builtin/commit.c
+++ b/builtin/commit.c
@@ -1402,6 +1402,7 @@ int run_commit_hook(int editor_is_used, const char *index_file, const char *name
 
 int cmd_commit(int argc, const char **argv, const char *prefix)
 {
+	const char *argv_gc_auto[] = {"gc", "--auto", NULL};
 	static struct wt_status s;
 	static struct option builtin_commit_options[] = {
 		OPT__QUIET(&quiet, N_("suppress summary after successful commit")),
@@ -1607,6 +1608,7 @@ int cmd_commit(int argc, const char **argv, const char *prefix)
 		     "not exceeded, and then \"git reset HEAD\" to recover."));
 
 	rerere(0);
+	run_command_v_opt(argv_gc_auto, RUN_GIT_CMD);
 	run_commit_hook(use_editor, get_index_file(), "post-commit", NULL);
 	if (amend && !no_post_rewrite) {
 		commit_post_rewrite(current_head, &oid);
-- 
2.15.1.424.g9478a66081