Subject: 29.0.50; diff-font-lock-prettify broken on new and deleted files

From: Matthias Meulien <[email-masked]>
Date: Sun, 26 Dec 2021 20:56:33 +0100

1. Configure Diff mode to enable font lock prettify:

(add-hook 'diff-mode-hook #'(lambda ()
			      (setq diff-font-lock-prettify t)))

2. Visit the recent change log of emacs sources (eg C-x v L when
visiting one of emacs source file)

3. Find commit 3d38d1d134 and call log-view-diff

4. Jump to line 245 for the chunk applying to lisp/sqlite.el

5. Observe the strange line:

new file   lisp/sqlite.ellisp/sqlite.el

where "new file   lisp/sqlite.el" is expected.

A similar problem can be observed for deleted files.

Proposed fixed (but I must confess I've no idea why the original code
tried to set two distinct overlays):

>From 0f9a40a1514fc5cf4e04bcdb69db7eb30dd0c6ba Mon Sep 17 00:00:00 2001
From: Matthias Meulien <[email-masked]>
Date: Sun, 26 Dec 2021 18:39:57 +0100
Subject: [PATCH] Fix diff--font-lock-prettify broken on created or deleted
 files

---
 lisp/vc/diff-mode.el | 24 +++++++++++-------------
 1 file changed, 11 insertions(+), 13 deletions(-)

diff --git a/lisp/vc/diff-mode.el b/lisp/vc/diff-mode.el
index 8f83aa580e..60d210ca22 100644
--- a/lisp/vc/diff-mode.el
+++ b/lisp/vc/diff-mode.el
@@ -2612,19 +2612,17 @@ diff--font-lock-prettify
                          "\\(?:index.*\n\\)?"
                          "--- \\(?:" null-device "\\|a/\\(.*\\)\\)\n"
                          "\\+\\+\\+ \\(?:" null-device "\\|b/\\(.*\\)\\)\n"))))
-        (put-text-property (match-beginning 0)
-                           (or (match-beginning 2) (match-beginning 1))
-                           'display (propertize
-                                     (cond
-                                      ((null (match-beginning 1))
-                                       (concat "new file  " (match-string 2)))
-                                      ((null (match-beginning 2))
-                                       (concat "deleted   " (match-string 1)))
-                                      (t
-                                       (concat "modified  " (match-string 1))))
-                                     'face '(diff-file-header diff-header)))
-        (put-text-property (match-end 1) (1- (match-end 0))
-                           'display ""))))
+        (put-text-property (match-beginning 0) (1- (match-end 0))
+                           'display
+                           (propertize
+                            (cond
+                             ((null (match-string 1))
+                              (concat "new file  " (match-string 2)))
+                             ((null (match-string 2))
+                              (concat "deleted  " (match-string 1)))
+                             (t
+                              (concat "modified  " (match-string 1))))
+                            'face '(diff-file-header diff-header))))))
   nil)
 
 ;;; Syntax highlighting from font-lock
-- 
2.30.2

In GNU Emacs 29.0.50 (build 1, x86_64-pc-linux-gnu, GTK+ Version 3.24.24, cairo version 1.16.0)
 of 2021-12-11 built on carbon
Repository revision: 15553f936abcc9c0bc85a2cd245319de273ee523
Repository branch: temp
Windowing system distributor 'The X.Org Foundation', version 11.0.12011000
System Description: Debian GNU/Linux 11 (bullseye)

Configured using:
 'configure --with-native-compilation'

Configured features:
ACL CAIRO DBUS FREETYPE GIF GLIB GMP GNUTLS GPM GSETTINGS HARFBUZZ JPEG
JSON LCMS2 LIBOTF LIBSELINUX LIBXML2 M17N_FLT MODULES NATIVE_COMP NOTIFY
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Important settings:
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  value of $XMODIFIERS: @im=ibus
  locale-coding-system: utf-8-unix

Major mode: Apropos

Minor modes in effect:
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/home/matthias/.config/emacs/elpa/dictionary-20201001.1727/dictionary hides /usr/local/share/emacs/29.0.50/lisp/net/dictionary

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dbusbind inotify lcms2 dynamic-setting system-font-setting
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Memory information:
((conses 16 1292883 149347)
 (symbols 48 43725 5)
 (strings 32 217988 10513)
 (string-bytes 1 9128224)
 (vectors 16 95840)
 (vector-slots 8 2474388 186797)
 (floats 8 754 1282)
 (intervals 56 118271 611)
 (buffers 992 242))

-- 
Matthias