Re: [PATCH v3 4/4] submodule: record superproject gitdir during 'update'

From: Derrick Stolee <stolee@gmail.com>
Date: Aug 20, 2021, 00:59 UTC
Message-ID: <66111c98-8be3-d3e5-288f-cb5b59744cb5@gmail.com>
In-Reply-To: <20210819200953.2105230-5-emilyshaffer@google.com>

On 8/19/2021 4:09 PM, Emily Shaffer wrote:

Show 8 quoted lines

> +		# Cache a pointer to the superproject's gitdir. This may have
> +		# changed, so rewrite it unconditionally. Writes it to worktree
> +		# if applicable, otherwise to local.
> +		relative_gitdir="$(git rev-parse --path-format=relative \
> +						 --prefix "${sm_path}" \
> +						 --git-dir)"
> +
> +		git -C "$sm_path" config --worktree \> +			submodule.superprojectgitdir "$relative_gitdir"

Ok, I see now why you care about the worktree config. The scenario you are covering is something like moving a submodule within a worktree and not wanting to change the relative path of other copies of that submodule within other worktrees, yes?

For commands such as 'init' and 'add', we don't have the possibility of colliding with other worktrees because the submodule is being created for the first time, so the relative path should be safe to place in the non-worktree config.

I do struggle with the fact that these are inconsistent across the two commits. It makes me think that there should only be one way to do it, and either the NEEDSWORK needs to be fixed now, or this line shouldn't include --worktree. Much of this can depend on the reason the worktree config exists for a submodule. I expect you have more context than me, so could you help me understand?

Moving to a different concern I am now realizing with this config: What happens if a submodule moves, and then a user runs 'git checkout' in the superproject to move it back? How do we make this config value update across those movements? Is there a possibility of integrating with unpack_trees() to notice that a submodule has moved and hence we should update this config value?

Thanks, -Stoolee