Re: Teach git-fetch(1) to use a quarantine directory

[Taylor Blau <me@ttaylorr.com>]

On Mon, Jul 17, 2023 at 12:48:17PM +0200, Toon Claes wrote:
> Hi,
>
> I've been looking into making git-fetch(1) to use a quarantine
> directory, but I'm a bit stuck on direction.

What are you hoping to accomplish? receive-pack quarantines its objects
to ensure that the pre-receive hook(s) are all OK before accepting the
push. See 722ff7f876c (receive-pack: quarantine objects until
pre-receive accepts, 2016-10-03) for more of the details there.

Are you suggesting that fetch be taught the same, so that we can
quarantine the pack sent from a remote before moving it into the main
repository?

> I took git-receive-pack(1) as an example how it uses a quarantine
> directory. It seems it sets the environment variables
> $GIT_OBJECT_DIRECTORY and $GIT_ALTERNATE_OBJECT_DIRECTORIES so the real
> object db is used as an alternative, and a temporary is set as the
> default. Then a sub-process is spawned to uses these. In case of
> git-receive-pack(1), it calls git-unpack-objects(1).
>
> At the moment git-fetch(1) does not spawn any similar subprocess, so if
> we want to take the same approach to use the quarantine, we'll need to
> split up that command.

That doesn't seem necessary, you can use `tmp_objdir_add_as_alternate()`
to register a temporary directory as an alternate. See the tmp-objdir.h
API for more convenience functions.

Thanks,
Taylor