master 7d42a76234e: * lisp/vc/vc.el (vc-deduce-backend-nonvc-modes): New variable (bug#67145).

[Juri Linkov]

branch: master
commit 7d42a76234ea5ca417915f8d5d755cc1f5aae7e5
Author: Juri Linkov <juri@linkov.net>
Commit: Juri Linkov <juri@linkov.net>

    * lisp/vc/vc.el (vc-deduce-backend-nonvc-modes): New variable (bug#67145).
    
    (vc-deduce-backend): Use it.
---
 lisp/vc/vc.el | 12 +++++++++---
 1 file changed, 9 insertions(+), 3 deletions(-)

diff --git a/lisp/vc/vc.el b/lisp/vc/vc.el
index 95f9218dcbf..d768af678c3 100644
--- a/lisp/vc/vc.el
+++ b/lisp/vc/vc.el
@@ -1071,14 +1071,20 @@ Within directories, only files already under version 
control are noticed."
 (defvar diff-vc-backend)
 (defvar diff-vc-revisions)
 
+;; Maybe we could even use comint-mode rather than shell-mode?
+(defvar vc-deduce-backend-nonvc-modes
+  '(dired-mode shell-mode eshell-mode compilation-mode)
+  "List of modes not supported by VC where backend should be deduced.
+In these modes the backend is deduced based on `default-directory'.
+When nil, the backend is deduced in all modes.")
+
 (defun vc-deduce-backend ()
   (cond ((derived-mode-p 'vc-dir-mode)   vc-dir-backend)
        ((derived-mode-p 'log-view-mode) log-view-vc-backend)
        ((derived-mode-p 'log-edit-mode) log-edit-vc-backend)
        ((derived-mode-p 'diff-mode)     diff-vc-backend)
-        ;; Maybe we could even use comint-mode rather than shell-mode?
-       ((derived-mode-p
-          'dired-mode 'shell-mode 'eshell-mode 'compilation-mode)
+       ((or (null vc-deduce-backend-nonvc-modes)
+            (apply #'derived-mode-p vc-deduce-backend-nonvc-modes))
         (ignore-errors (vc-responsible-backend default-directory)))
        (vc-mode (vc-backend buffer-file-name))))