(diff-find-file-name): Only accept regular files, to rule out

/dev/null, directories, etc.

lisp/ChangeLog

 2007-08-27  Glenn Morris  <rgm@gnu.org>
 
+	* diff-mode.el (diff-find-file-name): Only accept regular files,
+	to rule out /dev/null, directories, etc.
+
 	* vc-svn.el (vc-svn-diff): If the repository version of all the
 	files is the same as the specified OLDVERS, do a local diff.
 

lisp/diff-mode.el

@@ -682,7 +682,9 @@ PREFIX is only used internally: don't use it."
 	   ((or (null files)
 		(setq file (do* ((files files (cdr files))
 				 (file (car files) (car files)))
-			       ((or (null file) (file-exists-p file))
+			       ;; Use file-regular-p to avoid
+			       ;; /dev/null, directories, etc.
+			       ((or (null file) (file-regular-p file))
 				file))))
 	    file))
        ;; <foo>.rej patches implicitly apply to <foo>