Re: [PATCH v2 2/2] fix(gc): make --prune=now compatible with --expire-to

From: ZheNing Hu <adlternative@gmail.com>
Date: Jan 15, 2025, 07:56 UTC
Message-ID: <CAOLTT8TaDBtpgXRAj9yjiJB-h8vGjd6bEg29gOiOUwvQXbzZ3g@mail.gmail.com>
In-Reply-To: <20250113091750.GA794747@coredump.intra.peff.net>

Jeff King <peff@peff.net> 于2025年1月13日周一 17:17写道：

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>
> On Tue, Dec 31, 2024 at 02:18:33AM +0000, ZheNing Hu via GitGitGadget wrote:
>
> > diff --git a/builtin/gc.c b/builtin/gc.c
> > index 77904694c9f..8656e1caff0 100644
> > --- a/builtin/gc.c
> > +++ b/builtin/gc.c
> > @@ -433,7 +433,8 @@ static int keep_one_pack(struct string_list_item *item, void *data UNUSED)
> >  static void add_repack_all_option(struct gc_config *cfg,
> >                                 struct string_list *keep_pack)
> >  {
> > -     if (cfg->prune_expire && !strcmp(cfg->prune_expire, "now"))
> > +     if (cfg->prune_expire && !strcmp(cfg->prune_expire, "now")
> > +             && !(cfg->cruft_packs && cfg->repack_expire_to))
> >               strvec_push(&repack, "-a");
>
> I expected to see a mention of repack_expire_to here, but not
> cfg->cruft_packs. These two are AND-ed together so we are only disabling
> "repack -a" when both options ("--expire-to" and "--cruft") are passed.
> Can we --expire-to without cruft? I.e., what should happen with:
>
>   git gc --expire-to=some-path --prune=now --no-cruft
>
> Looking at the underlying git-repack, it seems that we only respect
> --expire-to at all when used with "--cruft", and don't otherwise
> consider it. Which is what the manpage says ("Only useful with --cruft
> -d").
>

Yes, this is the current state of git-repack. The --expire-to option can only be used with --cruft, which is why I use cruft_packs && repack_expire_to as a double safeguard.

When using --no-cruft, the option --expire-to becomes irrelevant. So leaving `git gc --prune=now` as is at this point: passing -a as a parameter to repack seems reasonable.

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> But if we look at this proposed patch for example:
>
>   https://lore.kernel.org/git/48438876fb42a889110e100a6c42ca84e93aac49.1733011259.git.me@ttaylorr.com/
>
> then it is expanding how --expire-to is used during the pruning step.
> OTOH, I think the way your patch 1 is structured means that we'd always
> pass --expire-to to git-repack anyway, and I _think_ even with the patch
> linked above that "repack -a -d --expire-to=whatever" would do the right
> thing.
>

I've taken a look at the patch, and I believe Taylor's changes are primarily aimed at extending the --expire-to functionality within the --cruft feature, rather than expecting --expire-to to be used on its own.

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> In which case the problem really is the combination of cruft packs and
> expire-to. Just cruft packs by themselves do not need to override using
> "-a" for "--prune=now" because we know that any such cruft pack would be
> empty.
>
> So I think this logic is correct. Taylor might have more thoughts,
> though (and ideas on whether he intends to revisit that earlier patch).
>
> I do think this change should probably be done as part of patch 1,
> rather than introducing a buggy state and then fixing it in patch 2.
>

Yes, I agree with that, and perhaps a single patch will suffice.

> -Peff

- ZheNing Hu