Support VC revisions in diff-goto-source (bug#33319)

* lisp/vc/diff-mode.el (diff-vc-revisions): New defvar.
(diff-find-source-location): Call vc-find-revision for
non-nil values of 'other', diff-vc-backend, diff-vc-revisions.

* lisp/vc/vc.el (vc-diff-internal): Set buffer-local
diff-vc-revisions to the list of used revisions.

* doc/emacs/files.texi (Diff Mode): Update diff-goto-source
for VC-related prefix argument.

1 files changed, 4 insertions, 0 deletions

diff --git a/etc/NEWS b/etc/NEWS
index 2f07abb4eb5..2a2010e9d36 100644
--- a/etc/NEWS
+++ b/etc/NEWS
@@ -368,6 +368,10 @@ To disable it, set the new defcustom 'diff-font-lock-refine' to nil.
 *** File headers can be shortened, mimicking Magit's diff format.
 To enable it, set the new defcustom 'diff-font-lock-prettify to t.
 
+*** Prefix arg of 'diff-goto-source' means jump to the old revision
+of the file under version control if point is on an old changed line,
+or to the new revision of the file otherwise.
+
 ** Browse-url
 
 *** The function 'browse-url-emacs' can now visit a URL in selected window.