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

From: Ævar Arnfjörð Bjarmason <[email-masked]>
Date: Thu, 11 Oct 2018 12:34:35 +0200

On Thu, Oct 11 2018, SZEDER Gábor wrote:

> On Thu, Oct 11, 2018 at 12:08:47PM +0200, Ævar Arnfjörð Bjarmason wrote:
>>
>> 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.
>
> How would that affect setups with 'gc.autoDetach = false', or, more
> importantly, platforms, where 'git gc --auto' always runs in the
> foreground?

I see we define NO_POSIX_GOODIES on Windows/MinGW, so those don't
demonize "gc", but then I'm confused by this which seems to imply the
opposite: https://github.com/Microsoft/vscode/issues/29901

As far as the general UI question goes, I think if you define
gc.autoDetach=true you're already OK with having "git fetch" and various
commands that produce commits block, so I don't see a big difference in
doing this in the middle of a rebase.

But it seems (aside from the question of how this is done on Windows)
that we demonize by default everywhere now, so I think it's OK to be
less conservative about where we run gc.

We also run a GC every 1000th commit in "git svn clone/rebase" already.