bug#51614: 29.0.50; [PATCH] vc-switches ignore file or directory variables

[Aleksandr Vityazev <avityazev@posteo.org>]

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Hello,

The current implementation of the vc-switches function from
lisp/vc/vc.el ignores the values ​​of vc-BACKEND-diff-switches,
vc-diff-switches set as local directory or file variables.

Here's a reproduction:

1. Run "emacs -Q"
2. "C-x C-f" to open file /tmp/test-project/.dir-locals.el
3. Type this into the buffer:
((nil ((vc-git-diff-switches . ("--binary" "--textconv")))))
4. "C-x C-s" to save the buffer
5. "C-x C-f" to open the file /tmp/test-project/test.gpg.
Without --binary and --textconv, diff will not be displayed
for a file with a .gpg extension.
6. Type something in the buffer for example: "Just a test"
7. "C-x C-s" to save the file
8. "C-x v v" to choose VCS backend: in this case, Git
and register the file under VCS
9. "C-x v v" to commit changes
10. Type commit message and "C-c C-c"
11. Type something in the buffer with file /tmp/test-project/test.gpg
12. "C-x C-s" to save the buffer
13. "C-x v =" to show the diff
14. Bug occurs: diff is not displayed.


Perhaps the attached patch can solve the problem.


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From 9b031423294224a6fe142abf6bd469b5cfa99c83 Mon Sep 17 00:00:00 2001
From: Alexandr Vityazev <avityazev@posteo.org>
Date: Thu, 28 Oct 2021 22:43:28 +0300
Subject: [PATCH] * lisp/vc/vc.el (vc-switches): Handle dir local variables.

* lisp/vc/vc.el (vc-switches): Handle vc-BACKEND-diff-switches,
vc-diff-switches set as local directory or file variables.
---
 lisp/vc/vc.el | 21 +++++++++++----------
 1 file changed, 11 insertions(+), 10 deletions(-)

diff --git a/lisp/vc/vc.el b/lisp/vc/vc.el
index 927a241a60..a858cbc451 100644
--- a/lisp/vc/vc.el
+++ b/lisp/vc/vc.el
@@ -1700,16 +1700,17 @@ diff only, `diff-switches'.
 If the chosen value is not a string or a list, return nil.
 This is so that you may set, e.g. `vc-svn-diff-switches' to t in order
 to override the value of `vc-diff-switches' and `diff-switches'."
-  (let ((switches
-	 (or (when backend
-	       (let ((sym (vc-make-backend-sym
-			   backend (intern (concat (symbol-name op)
-						   "-switches")))))
-		   (when (boundp sym) (symbol-value sym))))
-	     (let ((sym (intern (format "vc-%s-switches" (symbol-name op)))))
-	       (when (boundp sym) (symbol-value sym)))
-	     (cond
-	      ((eq op 'diff) diff-switches)))))
+  (let* ((buffer (other-buffer (current-buffer) t))
+         (switches
+	  (or (when backend
+	        (let ((sym (vc-make-backend-sym
+			    backend (intern (concat (symbol-name op)
+						    "-switches")))))
+		  (when (boundp sym) (buffer-local-value sym buffer))))
+	      (let ((sym (intern (format "vc-%s-switches" (symbol-name op)))))
+	        (when (boundp sym) (buffer-local-value sym buffer)))
+	      (cond
+	       ((eq op 'diff) diff-switches)))))
     (if (stringp switches) (list switches)
       ;; If not a list, return nil.
       ;; This is so we can set vc-diff-switches to t to override
-- 
2.33.1


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-- 
Best regards,
Aleksandr Vityazev