Subject: Re: [PATCH] revert & cherry-pick: run git gc --auto

From: Ævar Arnfjörð Bjarmason <[email-masked]>
Date: Thu, 11 Oct 2018 12:08:47 +0200

On Thu, Oct 11 2018, Phillip Wood wrote:

> Hi Ævar
>
> On 10/10/2018 20:35, Ævar Arnfjörð Bjarmason wrote:
>> Expand on the work started in 095c741edd ("commit: run git gc --auto
>> just before the post-commit hook", 2018-02-28) to run "gc --auto" in
>> more commands where new objects can be created.
>>
>> The notably missing commands are now "rebase" and "stash". Both are
>> being rewritten in C, so any use of "gc --auto" there can wait for
>> that.
>
> If cherry-pick, revert or 'rebase -i' edit the commit message then they
> fork 'git commit' so gc --auto will be run there anyway.

Yeah it seems I totally screwed up the testing for this patch, first it
doesn't even compile because I'm not including run-command.h, I *did*
fix that, but while wrangling a few things didn't commit that *sigh*.

And yeah, there's some invocations where we now run gc --auto twice,
i.e. if you do revert, but not revert --no-edit, and not on cherry-pick,
but on cherry-pick --edit.

So yeah, this really needs to be re-thought.

> I wonder if it would be better to call 'gc --auto' from sequencer.c at
> the end of a string of successful picks, that would cover cherry-pick,
> 'rebase -iu' and revert. With 'rebase -i' it might be nice to avoid
> calling 'gc --auto' until the very end, rather than every time we stop
> for an edit but that is probably more trouble than it is worth.

That seems a lot better indeed. I.e. running it from the sequencer. I do
wonder if there should be some smarts about running it in the middle of
a sequence, i.e. think of a case where we're rebasing 10k commits, which
is a gc need similar to what happens in the middle of "git svn
clone". So maybe something where we gc --auto in the sequencer for every
Nth commit, and at the end.

>
>>
>> Signed-off-by: Ævar Arnfjörð Bjarmason <[email-masked]>
>> ---
>>
>> After reading the "Users are encouraged to run this task..." paragraph
>> in the git-gc manpage I was wondering if due to gc --auto all over the
>> place now (including recently in git-commit with a patch of mine) if
>> we shouldn't change that advice.
>>
>> I'm meaning to send some doc changes to git-gc.txt, but in the
>> meantime let's address this low-hanging fruit of running gc --auto
>> when we revert or cherry-pick commits, which can like git-commit
>> create a significant amount of loose objects.
>>
>>  builtin/revert.c | 4 ++++
>>  1 file changed, 4 insertions(+)
>>
>> diff --git a/builtin/revert.c b/builtin/revert.c
>> index 9a66720cfc..1b20902910 100644
>> --- a/builtin/revert.c
>> +++ b/builtin/revert.c
>> @@ -209,6 +209,7 @@ int cmd_revert(int argc, const char **argv, const char *prefix)
>>  {
>>  	struct replay_opts opts = REPLAY_OPTS_INIT;
>>  	int res;
>> +	const char *argv_gc_auto[] = {"gc", "--auto", NULL};
>>
>>  	if (isatty(0))
>>  		opts.edit = 1;
>> @@ -217,6 +218,7 @@ int cmd_revert(int argc, const char **argv, const char *prefix)
>>  	res = run_sequencer(argc, argv, &opts);
>>  	if (res < 0)
>>  		die(_("revert failed"));
>> +	run_command_v_opt(argv_gc_auto, RUN_GIT_CMD);
>>  	return res;
>>  }
>>
>> @@ -224,11 +226,13 @@ int cmd_cherry_pick(int argc, const char **argv, const char *prefix)
>>  {
>>  	struct replay_opts opts = REPLAY_OPTS_INIT;
>>  	int res;
>> +	const char *argv_gc_auto[] = {"gc", "--auto", NULL};
>>
>>  	opts.action = REPLAY_PICK;
>>  	sequencer_init_config(&opts);
>>  	res = run_sequencer(argc, argv, &opts);
>>  	if (res < 0)
>>  		die(_("cherry-pick failed"));
>> +	run_command_v_opt(argv_gc_auto, RUN_GIT_CMD);
>>  	return res;
>>  }
>>