bug#47879: [PATCH] Ignore mode hooks when analysing diffs

[Philip Kaludercic]

This fixes a bug related to log-edit-generate-changelog-from-diff.

When I tried to invoke this command in a commit buffer, the error

     signal: Unmatched bracket or quote

was raised. The reason was that I added paredit-mode to
emacs-lisp-mode-hook, that when invoked calls check-parens. This raises
an error when the diff contains a partial s-expression, which is almost
always the case.

The least invasive approach I could come up with was to defer the mode
hooks. Most hooks should not have any effect on what
diff-add-log-current-defuns is doing, but I'm not sure if there are any
exceptions that I didn't think of.

-- 
        Philip K.

>From 6ce025a1c61912ee20083271e821878f049ac801 Mon Sep 17 00:00:00 2001
From: Philip K <philipk@posteo.net>
Date: Sun, 18 Apr 2021 20:40:16 +0200
Subject: [PATCH 3/4] Avoid calling mode hook when analysing diff

Author:
---
 lisp/vc/diff-mode.el | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/lisp/vc/diff-mode.el b/lisp/vc/diff-mode.el
index 2c72c45f4b..0b77ed11bc 100644
--- a/lisp/vc/diff-mode.el
+++ b/lisp/vc/diff-mode.el
@@ -2334,7 +2334,8 @@ diff-add-log-current-defuns
                         (if other-buf (set-buffer other-buf)
                           (set-buffer (generate-new-buffer " 
*diff-other-text*"))
                           (insert (if applied old-text new-text))
-                          (funcall (buffer-local-value 'major-mode buf))
+                          (delay-mode-vhooks
+                            (funcall (buffer-local-value 'major-mode buf)))
                           (setq other-buf (current-buffer)))
                         (goto-char (point-min))
                         (forward-line (+ =lines -1
-- 
2.30.2