Re: undo-information kept for *occur*

[martin rudalics]

> This is not correct, because it seems to leave buffer-undo-list
> permanently set to t.  That prevents undoing of changes made by hand
> by the user.
>

Locally binding `buffer-undo-list' around the `erase-buffer' in
`occur-1' is trivial.  But `occur-mode' has this

  (add-hook 'change-major-mode-hook 'font-lock-defontify nil t)

which means I would have to bind `buffer-undo-list' whenever I change
the major-mode for this buffer.  Locally bind `buffer-undo-list' around
`kill-all-local-variables' in `occur-mode'?