Clarify that 'diff-error' is part of Emacs 28.1

* lisp/vc/diff-mode.el (diff-error): Add :version tag (bug#44727).

diff --git a/lisp/vc/diff-mode.el b/lisp/vc/diff-mode.el
index 5aeb8feb99015e07a22e124919555577ec90da60..0a90613604778e91ef9084ab05fe424b1ab58dba 100644 (file)
--- a/lisp/vc/diff-mode.el
+++ b/lisp/vc/diff-mode.el
@@ -403,7 +403,8 @@ well."
   '((((class color))
      :foreground "red" :background "black" :weight bold)
     (t :weight bold))
-  "`diff-mode' face for error messages from diff.")
+  "`diff-mode' face for error messages from diff."
+  :version "28.1")
 
 (defconst diff-yank-handler '(diff-yank-function))
 (defun diff-yank-function (text)