bug#61817: 30.0.50; Project.el finds incorrect project roots in git worktrees

[Dmitry Gutov]

On 26/02/2023 18:23, Arthur Miller wrote:
> What actions trigger the bug:
>
> Two different, unrelated repositories with emacs source code tree. My tree(s)
> looks like this:
>
> ~/repos/emsrc/emacs/
> ~/repos/enacs-tests/emacs/
>
> Where in both the last "emacs/" is the Emacs source tree from main git
> repository.
>
> ~/repos/emsrc/emacs/  is the one I use for my "everyday" Emacs. I build Emacs 
> now
> and then once in a week or few weeks with a script, and I make each build in its
> own our-of-source worktree. The other one is one where I used to do some tests.
> It shouldn't matter since all worktrees are contained withing parent directory,
> which in one case is "emsrc" and in the other case "emacs-tests", but for some
> reason project.el sees the wrong one.
>
> 1. create two parent folders each one containing a copy of emacs sources
> 1. create out of source worktree for Emacs source under one of those
> 2. navigate to the worktree/lisp/progmodes
> 3. run M-: (project-known-project-roots)
>
> In my Emacs, I am in my currently installed emacs worktree, where git root is
>
> ~/repos/emsrc/emacs but project.el returns ("~/repos/emacs-tests/emacs/") as a
> result

What does (project-root (project-current)) return? And which dirs you 
are testing it in?

> I am not chasing the bug, but I don't see much code in project.el related
> to worktrees.

Normally, there shouldn't be any need to handle worktree specially: it 
contains a file called .git at the top which can serve as a marker just 
fine.

> The only place I see them mentioned is about submodules.I
> personally have used this one for quite some time, and it seems to correctly
> handle worktrees for me:

You code looks like it can return the "actual git root" that can be a 
directory residing somewhere else than the current directory tree. Is 
that what you wanted? Off the top of my head, that should break the 
'project-files' method.