(find-change-log): Try get-file-buffer before file-exists-p.

lisp/add-log.el

@@ -75,7 +75,7 @@ current buffer to the complete file name."
     ;; Move up in the dir hierarchy till we find a change log file.
     (let ((file1 file-name)
 	  parent-dir)
-      (while (and (not (file-exists-p file1))
+      (while (and (not (or (get-file-buffer file1) (file-exists-p file1)))
 		  (progn (setq parent-dir
 			       (file-name-directory
 				(directory-file-name
@@ -86,7 +86,7 @@ current buffer to the complete file name."
 	;; Move up to the parent dir and try again.
 	(setq file1 (expand-file-name (change-log-name) parent-dir)))
       ;; If we found a change log in a parent, use that.
-      (if (file-exists-p file1)
+      (if (or (get-file-buffer file1) (file-exists-p file1))
 	  (setq file-name file1)))
     ;; Make a local variable in this buffer so we needn't search again.
     (set (make-local-variable 'change-log-default-name) file-name)