Subject: Re: [PATCH v3 6/8] gc: add `gc.repackFilter` config option

From: Taylor Blau <[email-masked]>
Date: Tue, 25 Jul 2023 19:07:57 -0400

On Mon, Jul 24, 2023 at 10:59:07AM +0200, Christian Couder wrote:
> A previous commit has implemented `git repack --filter=<filter-spec>` to
> allow users to filter out some objects from the main pack and move them
> into a new different pack.
>
> Users might want to perform such a cleanup regularly at the same time as
> they perform other repacks and cleanups, so as part of `git gc`.
>
> Let's allow them to configure a <filter-spec> for that purpose using a
> new gc.repackFilter config option.

Makes sense.

> Now when `git gc` will perform a repack with a <filter-spec> configured
> through this option and not empty, the repack process will be passed a
> corresponding `--filter=<filter-spec>` argument.

I may be missing something, but what happens if the user has configured
gc.repackFilter, but passes additional filters over the command-line
arguments? I'm not sure whether these should be AND'd with the existing
filters in config, or if they should reset them to zero, or something
else.

Regardless, I think it would be beneficial to users if we spelled this
out in git-gc(1) instead of just this patch message here.

> diff --git a/t/t6500-gc.sh b/t/t6500-gc.sh
> index 69509d0c11..5b89faf505 100755
> --- a/t/t6500-gc.sh
> +++ b/t/t6500-gc.sh
> @@ -202,6 +202,18 @@ test_expect_success 'one of gc.reflogExpire{Unreachable,}=never does not skip "e
>  	grep -E "^trace: (built-in|exec|run_command): git reflog expire --" trace.out
>  '
>
> +test_expect_success 'gc.repackFilter launches repack with a filter' '
> +	test_when_finished "rm -rf bare.git" &&
> +	git clone --no-local --bare . bare.git &&
> +
> +	git -C bare.git -c gc.cruftPacks=false gc &&
> +	test_stdout_line_count = 1 ls bare.git/objects/pack/*.pack &&
> +
> +	GIT_TRACE=$(pwd)/trace.out git -C bare.git -c gc.repackFilter=blob:none -c repack.writeBitmaps=false -c gc.cruftPacks=false gc &&

Nit: can we wrap this across multiple lines?

> +	test_stdout_line_count = 2 ls bare.git/objects/pack/*.pack &&
> +	grep -E "^trace: (built-in|exec|run_command): git repack .* --filter=blob:none ?.*" trace.out
> +'

I think the `test_subcommand` helper might work here, and it would allow
you to avoid writing a long grep invocation.

Thanks,
Taylor