Is there any way to have Emacs save your undo history between sessions?

Question

Is there any way to have EMACS save your undo history between sessions?

I\'m aware of the savehist lib, the saveplace lib, the desktop lib, and the windows lib, thes

Answer 1

I have managed to get the undo history working by using the information provided here: http://emacs.stackexchange.com/q/3725/2287

Instead of patching the original file desktop.el.gz I created an advice that temporarily overrides (buffer-local-variables) then I use it together with the function that gathers information about the buffer.

(defun +append-buffer-undo-list-to-buffer-local-variables-advice (orig-fn &rest args)
  "Override `buffer-local-variables' and call ORIG-FN with ARGS.
There is a bug in Emacs where the `buffer-undo-list' data is
missing from the output of `buffer-local-variables'. This
advice temporarily overrides the function and appends the
missing data."
  (let ((orig-buffer-local-variables-fn (symbol-function 'buffer-local-variables)))
    (cl-letf (((symbol-function 'buffer-local-variables)
               #'(lambda () (append (funcall orig-buffer-local-variables-fn)
                               `(,(cons 'buffer-undo-list buffer-undo-list))))))
      (apply orig-fn args))))

(advice-add #'desktop-buffer-info :around #'+append-buffer-undo-list-to-buffer-local-variables-advice)
(push 'buffer-undo-list desktop-locals-to-save)
(desktop-save-mode 1)

I hope this helps someone else.