Re: [PATCH v1] worktree: set worktree environment in post-checkout hook

From: Eric Sunshine <sunshine@sunshineco.com>
Date: Feb 12, 2018, 03:27 UTC
Message-ID: <CAPig+cQ7MRQVT-1yNF8t6RMHNrgMtYvzOToamaLO==ymxTtLYg@mail.gmail.com>
In-Reply-To: <20180210010132.33629-1-lars.schneider@autodesk.com>

On Fri, Feb 9, 2018 at 8:01 PM,  <lars.schneider@autodesk.com> wrote:

Show 14 quoted lines

> In ade546be47 (worktree: invoke post-checkout hook (unless
> --no-checkout), 2017-12-07) we taught Git to run the post-checkout hook
> in worktrees. Unfortunately, the environment of the hook was not made
> aware of the worktree. Consequently, a 'git rev-parse --show-toplevel'
> call in the post-checkout hook would return a wrong result.
>
> Fix this by setting the 'GIT_WORK_TREE' environment variable to make
> Git calls within the post-checkout hook aware of the worktree.
>
> Signed-off-by: Lars Schneider <larsxschneider@gmail.com>
> ---
> I think this is a bug in Git 2.16. We noticed it because it caused a
> problem in Git LFS [1]. The modified test case fails with Git 2.16 and
> succeeds with this patch.

Thanks for reporting and diagnosing the problem.

I have some concerns about this patch's fix of setting GIT_WORK_TREE unconditionally. In particular, such unconditional setting of GIT_WORK_TREE might cause unforeseen problems. Although the circumstances may not be quite the same, but the tale told by 86d26f240f (setup.c: re-fix d95138e (setup: set env $GIT_WORK_TREE when .., 2015-12-20) makes me cautious.

More significantly, though, setting GIT_WORK_TREE seems too specialized a solution. While it may "fix" Git commands invoked by the hook, it does nothing for other commands ('cp', 'mv', etc.) which the hook may employ.

As a review comment, I was going to suggest that you chdir() to the new worktree directory instead of messing with GIT_WORK_TREE, but when I tested it myself before making the suggestion, I discovered that the issue is a bit more involved. The result is that I ended up posting a patch series[1] to replace this one, with what I believe is a more correct fix.

[1]: https://public-inbox.org/git/20180212031526.40039-1-sunshine@sunshineco.com/