vc-derived-from-dir-mode subject to infinite recursion.

[David Koppelman]

The following fixes the infinite recursion in vc mode
encountered when requesting a diff from a log file. Is it that simple?

--- vc.el.~1.672.~      2008-05-19 09:54:22.000000000 -0500
+++ vc.el       2008-05-21 10:36:59.000000000 -0500
@@ -998,7 +998,7 @@ Within directories, only files already u
 
 (defun vc-derived-from-dir-mode (&optional buffer)
   "Are we in a VC-directory buffer, or do we have one as an ancestor?"
-  (let ((buffer (or buffer (current-buffer))))
+  (with-current-buffer (or buffer (current-buffer))
     (cond ((derived-mode-p 'vc-dir-mode) t)
          (vc-parent-buffer (vc-derived-from-dir-mode vc-parent-buffer))
          (t nil))))