Re: packObjectsHook and the git executable

From: Jeff King <peff@peff.net>
Date: Jan 30, 2020, 07:11 UTC
Message-ID: <20200130071102.GA2189233@coredump.intra.peff.net>
In-Reply-To: <CAGyf7-E==gzsvP-ckK0kwHD+f9pMmLBVpL4y2rC9tqk7ZiuW1g@mail.gmail.com>

On Wed, Jan 29, 2020 at 05:00:18PM -0800, Bryan Turner wrote:

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> In upload-pack.c, when Git invokes the packObjectsHook, it's
> hard-coded to pass "git". Unless it modifies the PATH environment
> variable, though, if the script were to invoke the provided command
> line as-is, it may end up running a different version of Git than the
> version being used to run upload-pack (or http-backend).

We do modify PATH to put git's exec-path at the start. This happens in setup_path(), which is called by the main "git" executable (so "git upload-pack" before it hits cmd_upload_pack()).

Programs which are invoked directly as "git-upload-pack" need to call that function on their own (which happens when upload-pack is invoked over ssh). But upload-pack and http-backend do that.

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> Is there any way the packObjectsHook could be passed the "right" git
> executable? Or am I missing some surrounding context that means
> executing "git" is somehow guaranteed to invoke the "right" binary?
> (Perhaps this same PATH-related caveat applies to other places where
> Git invokes itself recursively?)

I think all is working as designed, but if you have a reproducible case where we run the "wrong" git, I can take a look at it.

-Peff