gistfile1.txt

(defun undo-only (&optional arg)
  "Undo some previous changes.
Repeat this command to undo more changes.
A numeric ARG serves as a repeat count.
Contrary to `undo', this will not redo a previous undo."
  (interactive "*p")
  (let ((undo-no-redo t))
    (undo arg)
    ;; assume undo succeeded and overwrite 
    ;; what it wrote.
    (message "%s" (if (or (region-active-p) (and arg (not (numberp arg))))
                      "Undo in region!"
                    "Undo!"))))