Reverting but keeping undo

[Óscar Fuentes]

`revert-buffer' discards undo history. I can understand that undo
history might be in conflict with the new contents of the buffer. How
dangerous is that? Apart from that, what could be wrong with using the
recipe published in

http://www.emacswiki.org/emacs/RevertBuffer#toc4

?

For your convenience, this is the recipe:

(defun revert-buffer-keep-undo (&rest -)
  "Revert buffer but keep undo history."
  (interactive)
  (let ((inhibit-read-only t))
    (erase-buffer)
    (insert-file-contents (buffer-file-name))
    (set-visited-file-modtime (visited-file-modtime))
    (set-buffer-modified-p nil)))

Install in command ‘revert-buffer’ with

  (setq revert-buffer-function 'revert-buffer-keep-undo)