Re: [PATCH v2] githooks: discuss Git operations in foreign repositories

From: Jeff King <peff@peff.net>
Date: Jan 11, 2023, 19:01 UTC
Message-ID: <Y78Hgj4jKga7vNo7@coredump.intra.peff.net>
In-Reply-To: <pull.1457.v2.git.1673293508399.gitgitgadget@gmail.com>

On Mon, Jan 09, 2023 at 07:45:08PM +0000, Eric Sunshine via GitGitGadget wrote:

Show 15 quoted lines

> Recommended best-practice[1,2,3,4,5,6] for avoiding this problem is for
> the hook to ensure that Git variables are unset before invoking Git
> commands in foreign repositories or other worktrees:
> 
>     unset $(git rev-parse --local-env-vars)
> 
> However, this advice is not documented anywhere. Rectify this
> shortcoming by mentioning it in githooks.txt documentation.
> 
> [1]: https://lore.kernel.org/git/YFuHd1MMlJAvtdzb@coredump.intra.peff.net/
> [2]: https://lore.kernel.org/git/20200228190218.GC1408759@coredump.intra.peff.net/
> [3]: https://lore.kernel.org/git/20190516221702.GA11784@sigill.intra.peff.net/
> [4]: https://lore.kernel.org/git/20190422162127.GC9680@sigill.intra.peff.net/
> [5]: https://lore.kernel.org/git/20180716183942.GB22298@sigill.intra.peff.net/
> [6]: https://lore.kernel.org/git/20150203163235.GA9325@peff.net/

Boy, I'm like a broken record.

The patch here looks good to me. The problem is wider than just hooks, but it seems like that's going to be a common place for people to get caught by it. So certainly this is going in the right direction.

The other place I've run into it is writing a script meant to be run as an external command. E.g., running this:

  git --git-dir=/some/path my-external-command

means that "my-external-command" is going to have $GIT_DIR set. If it wants to operate on another repository it needs to take care to clear that from the environment.

-Peff