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Re: Regression: submodule worktrees can clobber core.worktree config

On Tue, Jan 8, 2019 at 2:16 PM Tomasz Śniatowski <tsniatowski@xxxxxxxx> wrote:
> After upgrading to 2.20.1 I noticed in some submodule+worktree scenarios git
> will break the submodule configuration. Reproducible with:
>     git init a && (cd a; touch a; git add a; git commit -ma)
>     git init b && (cd b; git submodule add ../a; git commit -mb)
>     git -C b worktree add ../b2
>     git -C b/a worktree add ../../b2/a
>     git -C b status
>     git -C b2 submodule update
>     git -C b status
> The submodule update in the _worktree_ puts an invalid core.worktree value in
> the _original_ repository submodule config (b/.git/modules/a/config), causing
> the last git status to error out with:
>     fatal: cannot chdir to '../../../../../../b2/a': No such file or directory
>     fatal: 'git status --porcelain=2' failed in submodule a
> Looking at the config file itself, the submodule update operation applies the
> following change (the new path is invalid):
>     -       worktree = ../../../a
>     +       worktree = ../../../../../../b2/a
> This worked fine on 2.19.2 (no config change, no error), and was useful to have
> a worktree with (large) submodules that are also worktrees.

Thanks for reporting the issue!

> Bisects down to:
> 74d4731da1 submodule--helper: replace connect-gitdir-workingtree by
> ensure-core-worktree

So this would need to update the worktree config, not the generic config.

We'd need to replace the line
    cfg_file = repo_git_path(&subrepo, "config");
in builtin/submodule--helper.c::ensure_core_worktree()
to be a worktree specific call.

Or the other way round we'd want to make repo_git_path to
be worktree specific and introduce repo_common_path for
the main working tree.

Looking at Duys tree,
is pretty much what we need.

Reverting that topic that introduced this (4d6d6e,
Merge branch 'sb/submodule-update-in-c'), might be possible but
that would conflict with another followup that fixes issues in
that series
(see sb/submodule-unset-core-worktree-when-worktree-is-lost
so I'd rather just cherry-pick the commit from Duy.