>From 8ef441e5d5340b06dd04d294a384ae05bf7f5615 Mon Sep 17 00:00:00 2001
From: Philip Kaludercic <philipk@posteo.net>
Date: Tue, 6 Sep 2022 22:06:29 +0200
Subject: [PATCH] Add new user option 'diff-add-log-use-relative-names'

* .dir-locals.el: Set 'diff-add-log-use-relative-names' to t
* etc/NEWS: Mention 'diff-add-log-relative-names'
* lisp/vc/diff-mode.el (diff-add-log-use-relative-names): Add new option.
(diff-add-log-current-defuns): Use new option.
---
 .dir-locals.el       |  3 ++-
 etc/NEWS             |  5 +++++
 lisp/vc/diff-mode.el | 20 ++++++++++++++++++--
 3 files changed, 25 insertions(+), 3 deletions(-)

diff --git a/.dir-locals.el b/.dir-locals.el
index 1c90ddcf56..9882a19f85 100644
--- a/.dir-locals.el
+++ b/.dir-locals.el
@@ -5,7 +5,8 @@
          (sentence-end-double-space . t)
          (fill-column . 70)
 	 (emacs-lisp-docstring-fill-column . 65)
-         (bug-reference-url-format . "https://debbugs.gnu.org/%s")))
+         (bug-reference-url-format . "https://debbugs.gnu.org/%s")
+	 (diff-add-log-use-relative-names . t)))
  (c-mode . ((c-file-style . "GNU")
             (c-noise-macro-names . ("INLINE" "ATTRIBUTE_NO_SANITIZE_UNDEFINED" "UNINIT" "CALLBACK" "ALIGN_STACK"))
             (electric-quote-comment . nil)
diff --git a/etc/NEWS b/etc/NEWS
index b61b88d6fb..76c66a8e39 100644
--- a/etc/NEWS
+++ b/etc/NEWS
@@ -1340,6 +1340,11 @@ Sets the value of the buffer-local variable 'whitespace-style' in
 'diff-mode' buffers.  By default, this variable is '(face trailing)',
 which preserves behavior from previous Emacs versions.
 
++++
+*** New user option 'diff-add-log-use-relative-names'.
+If non-nil insert file names in ChangeLog skeletons relative to the
+VC root directory.
+
 ** Ispell
 
 ---
diff --git a/lisp/vc/diff-mode.el b/lisp/vc/diff-mode.el
index a01943437c..1d2fbca0e5 100644
--- a/lisp/vc/diff-mode.el
+++ b/lisp/vc/diff-mode.el
@@ -2336,10 +2336,21 @@ diff-undo
   (let ((inhibit-read-only t))
     (undo arg)))
 
+(defcustom diff-add-log-use-relative-names nil
+  "Use relative file names when generating ChangeLog skeletons.
+The files will be relative to the root directory of the VC
+repository.  This option affects the behaviour of
+`diff-add-log-current-defuns'."
+  :type 'boolean
+  :safe #'booleanp
+  :version "29.1")
+
 (defun diff-add-log-current-defuns ()
   "Return an alist of defun names for the current diff.
 The elements of the alist are of the form (FILE . (DEFUN...)),
-where DEFUN... is a list of function names found in FILE."
+where DEFUN... is a list of function names found in FILE.  If
+`diff-add-log-use-relative-names' is non-nil, file names in the alist
+are relative to the root directory of the VC repository."
   (save-excursion
     (goto-char (point-min))
     (let* ((defuns nil)
@@ -2373,7 +2384,12 @@ diff-add-log-current-defuns
           ;; hunks (e.g., "diff --git ..." etc).
           (re-search-forward diff-hunk-header-re nil t)
         (setq hunk-end (save-excursion (diff-end-of-hunk)))
-        (pcase-let* ((filename (substring-no-properties (diff-find-file-name)))
+        (pcase-let* ((filename (substring-no-properties
+                                (if diff-add-log-use-relative-names
+                                    (file-relative-name
+                                     (diff-find-file-name)
+                                     (vc-root-dir))
+                                  (diff-find-file-name))))
                      (=lines 0)
                      (+lines 0)
                      (-lines 0)
-- 
2.30.2