bug#28852: make revert-buffer ('g') in VC diff buffers keep point

[Juri Linkov <juri@linkov.net>]

>> This will restore point to the same point it was before...  but not to
>> "where it was", necessarily, I think?
>
> I was confused about how these functions worked.  I've respun the patch
> for Emacs 29, and it seem to work very well, so I've now pushed it.

This doesn't work with such customization:

  (add-hook 'diff-mode-hook 'rename-uniquely)

because this change assumes that the current buffer is always "*vc-diff*"
whereas the reverted buffer can be "*vc-diff*<2>".

Isn't the reverted buffer always current during revert-buffer command?
If this assumption is correct, how about his fix?

diff --git a/lisp/vc/vc.el b/lisp/vc/vc.el
index 0096a5fcb3..1671f2f860 100644
--- a/lisp/vc/vc.el
+++ b/lisp/vc/vc.el
@@ -1798,10 +1798,9 @@ vc-diff-internal
 	 (coding-system-for-read
 	  (if files (vc-coding-system-for-diff (car files)) 'undecided))
          (orig-diff-buffer-clone
-          (if (and (get-buffer buffer) revert-buffer-in-progress-p)
-              (with-current-buffer buffer
-                (clone-buffer
-                 (generate-new-buffer-name " *vc-diff-clone*") nil)))))
+          (if revert-buffer-in-progress-p
+              (clone-buffer
+               (generate-new-buffer-name " *vc-diff-clone*") nil))))
     ;; On MS-Windows and MS-DOS, Diff is likely to produce DOS-style
     ;; EOLs, which will look ugly if (car files) happens to have Unix
     ;; EOLs.
--