bug#68174: 30.0.50; Project and VC disagree about what repository we're in

[Dmitry Gutov <dmitry@gutov.dev>]

Hi!

On 31/12/2023 15:26, Sean Whitton wrote:
> X-debbugs-cc:juri@linkov.net
> 
> Hello,
> 
> 1. emacs -q
> 2. (setopt vc-deduce-backend-nonvc-modes t)
> 3. C-x C-f ~/src/dotfiles/.emacs.d/init.el RET
> 4. C-x p p ~/src/emacs/  RET o C-x v L
> 5. (project-root (project-current)) => "~/src/emacs/"
> 6. C-x v +
>     - git pull is attempted in ~/src/dotfiles/.
> 
> You're in a*vc-change-log*  for emacs.git, and (project-current) returns
> the correct project.  But C-x v + operates in ~/src/dotfiles/.

Thanks for the report.

I general, the problem looks unsolvable (or at least hard) because 
various VC-related buffers look back on the fileset that spawned them 
through the variable vc-parent-buffer. And that one is often just set to 
the buffer that was previous before the current one was created (in 
vc-setup-buffer).

This particular case though seems fixed with this patch, please test:

diff --git a/lisp/vc/vc.el b/lisp/vc/vc.el
index 3cd835a9d6b..82051740b8f 100644
--- a/lisp/vc/vc.el
+++ b/lisp/vc/vc.el
@@ -1074,6 +1074,7 @@ vc-expand-dirs

  (defvar vc-dir-backend)
  (defvar log-view-vc-backend)
+(defvar log-view-vc-fileset)
  (defvar log-edit-vc-backend)
  (defvar diff-vc-backend)
  (defvar diff-vc-revisions)
@@ -1155,6 +1156,8 @@ vc-deduce-fileset
  	      (vc-state buffer-file-name)
  	      (vc-checkout-model backend buffer-file-name))
  	(list backend (list buffer-file-name))))
+     ((derived-mode-p 'log-view-mode)
+      (list log-view-vc-backend log-view-vc-fileset))
       ((and (buffer-live-p vc-parent-buffer)
             ;; FIXME: Why this test?  --Stef
             (or (buffer-file-name vc-parent-buffer)