Re: Weird output of git status in pre-commit hook when providing a pathspec on commit

From: Michaël Fortin <fortinmike@gmail.com>
Date: Feb 4, 2015, 22:45 UTC
Message-ID: <FBB67809-5585-4D53-BF55-53248FD1369F@gmail.com>
In-Reply-To: <20150203163235.GA9325@peff.net>

Interesting!

Thanks for the info; unsetting git environment variables as you suggested fixes my issue on OS X (and Linux I suppose). I’m going to try this on Windows soon. Would that work as-is on Windows, or would I need to unset the vars using some other Windows-specific syntax?

Yes, I looked at the documentation for “-C", and “-o". Because this issue is triggered by the use of “-o”, maybe the appropriate place to mention this behaviour would be in the documentation for “-o”? I don’t know.

Thanks again,

Michaël Fortin www.irradiated.net

Show 60 quoted lines

> On Feb 3, 2015, at 11:32 AM, Jeff King <peff@peff.net> wrote:
> 
> On Tue, Feb 03, 2015 at 08:14:06AM -0500, Michaël Fortin wrote:
> 
>> Repo1 has the following pre-commit hook:
>> 
>> #!/bin/bash
>> git -C "../Repo2" status --porcelain
>> 
>> I then commit in Repo1 using the following (this is actually ran by a
>> GUI, I have no control over the commands themselves):
>> 
>> git add --force -- MyNewFile
>> git commit -m "My message" -o -- MyNewFile
> 
> Because the commit command uses "-o", git must use a temporary index
> file to stage the commit. It sets GIT_INDEX_FILE in the environment, and
> then runs your hook.
> 
> When the hook runs "git -C" it moves into another repository, but the
> GIT_INDEX_FILE in the environment takes precedence over the local index
> found in that repository. So you see a HEAD and working tree from Repo2,
> but the index from Repo1.
> 
> This is a specific case of a more general problem. If you were to run
> git like:
> 
>  git --git-dir=/path/to/.git commit ...
> 
> you would have similar problems. You would have $GIT_DIR set in the
> environment, and would see the HEAD from Repo1, but the working tree
> from Repo2.
> 
> In other words, moving into another git directory from inside a hook is
> not as easy as just going there. You also need to clear any state from
> the environment. E.g., by adding this to the top of your hook:
> 
>  unset $(git rev-parse --local-env-vars)
> 
> Should "-C" (or "--git-dir") make this easier by doing it for you? I'm
> not sure it is a good idea. It is right now valid to do:
> 
>  GIT_INDEX_FILE=/path/to/index.tmp git -C /path/to/repo ...
> 
> which would break if we cleared git variables. OTOH, maybe using "-C"
> (instead of chdir-ing yourself) is a good indication that you want that
> cleared. I dunno. It is probably too late at this point, as we would be
> subtly breaking backwards compatibility. Perhaps it would make more
> sense to add a new option, so you could do:
> 
>  git --reset-git-vars -C ../Repo2 status --porcelain
> 
> But this is a fairly obscure use case, and the rev-parse invocation
> above is not so bad. I think it is more about knowing that you need to
> use it, rather than the pain of typing it. And I am not sure how to make
> that more clear. Is there a specific place in the documentation you
> looked and might have been warned? Maybe the description for "-C" should
> cover this.
> 
> -Peff