Re: [git-users] Problem using detached worktrees with commands implemented in scripts

From: Dale R. Worley <worley@alum.mit.edu>
Date: Oct 21, 2013, 18:51 UTC
Message-ID: <201310211851.r9LIpOaH000372@freeze.ariadne.com>
In-Reply-To: <xmqqy55qurmf.fsf@gitster.dls.corp.google.com>

> From: Junio C Hamano <gitster@pobox.com>

> > ... it's not clear why GIT_WORK_TREE exists, ...
> 
> The configuration item came _way_ later than the environment, and we
> need to keep users and scripts from old world working, that is why.

OK, that explains a great deal. IIRC, I first became aware that detached worktrees are possible through the documentation of core.worktree. As Git's architecture has a tight binding between the repository and the worktree, it made a great deal of sense to me that the repository points to the detached worktree. And the absence of core.worktree, a non-detached worktree, is essentially equivalent to having core.worktree specify the directory containing the .git directory.

So the obvious way (to me) to invoke Git with a detached worktree is to set GIT_DIR to point to the repository, and the repository points to the root of the worktree. If the command operates on the worktree, Git can compare the cwd with the worktree root to determine the relative path of files.

(And you can see that in this situation, Git doesn't have to search upward to try to determine where the worktree root is.)

What you're saying is that there's an older mode of operation where the repository does not point to the worktree. Instead, the caller has to set GIT_DIR to locate the repository and GIT_WORK_TREE to locate the worktree. This would be prone to error, because the user is responsible for always pairing the repository with the correct worktree; it doesn't enforce the architectural assumption that the repository is paired with a work tree.

Dale