Worktree "gitdir" file being mangled after upgrade to 2.7.0

> Since upgrading to 2.7.0 last week, eventually I'll get to a point when
> I run 'git worktree list' where several worktrees are incorrectly
> reported as pointing to my main git checkout. Further analysis of the
> files in $GIT_DIR/worktrees/worktree_name/ shows that the gitdir file
> for the worktrees which display incorrectly contains ".git" instead of
> what it should contain (i.e. "/path/to/worktree/.git".
>
> This was reported a couple days ago on Github:
>
> https://github.com/git/git-scm.com/issues/650
>
> Since the audiences for the mailing list and Github don't overlap
> completely, I figured I'd report it here to get this issue in front of
> as many eyes as possible.

> Erik Johnson <palehose@gmail.com> writes:
>
>> Since upgrading to 2.7.0 last week, eventually I'll get to a point when
>> I run 'git worktree list' where several worktrees are incorrectly
>> reported as pointing to my main git checkout. Further analysis of the
>> files in $GIT_DIR/worktrees/worktree_name/ shows that the gitdir file
>> for the worktrees which display incorrectly contains ".git" instead of
>> what it should contain (i.e. "/path/to/worktree/.git".
>>
>> This was reported a couple days ago on Github:
>>
>> https://github.com/git/git-scm.com/issues/650
>>
>> Since the audiences for the mailing list and Github don't overlap
>> completely, I figured I'd report it here to get this issue in front of
>> as many eyes as possible.
>
> Thanks for relaying.  Duy, Michael, I think this is your area?

> On Thu, Jan 14, 2016 at 9:36 AM, Junio C Hamano <gitster@pobox.com> wrote:
>> Erik Johnson <palehose@gmail.com> writes:
>>
>>> Since upgrading to 2.7.0 last week, eventually I'll get to a point when
>>> I run 'git worktree list' where several worktrees are incorrectly
>>> reported as pointing to my main git checkout. Further analysis of the
>>> files in $GIT_DIR/worktrees/worktree_name/ shows that the gitdir file
>>> for the worktrees which display incorrectly contains ".git" instead of
>>> what it should contain (i.e. "/path/to/worktree/.git".
>>>
>>> This was reported a couple days ago on Github:
>>>
>>> https://github.com/git/git-scm.com/issues/650
>>>
>>> Since the audiences for the mailing list and Github don't overlap
>>> completely, I figured I'd report it here to get this issue in front of
>>> as many eyes as possible.
>>
>> Thanks for relaying.  Duy, Michael, I think this is your area?
>
> The only place that a relative path can be written is
> update_linked_girdir() unless i'm mistaken. That function is being
> deleted "soon" because it causes another problem

>>> Thanks for relaying.  Duy, Michael, I think this is your area?
>>
>> The only place that a relative path can be written is
>> update_linked_girdir() unless i'm mistaken. That function is being
>> deleted "soon" because it causes another problem
>
> `git worktree list` command does not modify the worktree gitdir file,
> so this is only a symptom of the problem.  If at all possible, we
> should move to get Duy's fix into the 2.7.1 release.  This problem
> almost makes git worktree list useless.

> Since upgrading to 2.7.0 last week, eventually I'll get to a point when
> I run 'git worktree list' where several worktrees are incorrectly
> reported as pointing to my main git checkout. Further analysis of the
> files in $GIT_DIR/worktrees/worktree_name/ shows that the gitdir file
> for the worktrees which display incorrectly contains ".git" instead of
> what it should contain (i.e. "/path/to/worktree/.git".