bug#60897: 29.0.60; vc-revert fails to revert buffer

[Eli Zaretskii <eliz@gnu.org>]

> Cc: 60897@debbugs.gnu.org
> From: Juri Linkov <juri@linkov.net>
> Date: Sun, 22 Jan 2023 19:17:21 +0200
> 
> > But as you noticed it doesn't refresh the buffer.  This is because
> > vc-deduce-fileset in the diff buffer now returns relative file names,
> > not absolute as vc-resynch-buffer expects.
> >
> > Expanding relative file names to absolute is not possible in
> > diff-vc-deduce-fileset, because then C-x v v will fail in
> > vc-default-checkin-patch that expects relative file names.
> >
> > So I think the right place to do this is before trying to compare
> > relative names with (string= buffer-file-name file):
> >
> > diff --git a/lisp/vc/vc-dispatcher.el b/lisp/vc/vc-dispatcher.el
> > @@ -643,6 +643,8 @@ vc-resynch-buffers-in-directory
> >  
> >  (defun vc-resynch-buffer (file &optional keep noquery reset-vc-info)
> >    "If FILE is currently visited, resynch its buffer."
> > +  (unless (file-name-absolute-p file)
> > +    (setq file (expand-file-name file (vc-root-dir))))
> >    (if (string= buffer-file-name file)
> >        (vc-resynch-window file keep noquery reset-vc-info)
> >      (if (file-directory-p file)
> 
> Eli, is this ok for the emacs-29 branch?  I'm unsure because
> vc-resynch-buffer is used in too many places, so this change
> is not localized to vc-revert.

You could use the expanded file name only for the purposes of the
string= call, no?  Then the effect of this change would be very local
and thus safer.