Re: undo-information kept for *occur*

[martin rudalics]

> Emacs turns off undo data generation while computing the *occur* buffer:
>
>     (defun occur-engine (regexp buffers out-buf nlines case-fold-search
>                            title-face prefix-face match-face keep-props)
>       (with-current-buffer out-buf
>    (let ((globalcount 0)
>          ;; Don't generate undo entries for creation of the initial contents.
>          (buffer-undo-list t)
>          (coding nil))
>          ...
>
> So why does it build up a lot of undo records?

I think most of them come from `erase-buffer' in `occur-1' (`occur-mode'
sets `buffer-undo-list' to nil).  `font-lock-defontify' should add some
too.