Re: The *Warnings* buffer and undo

[Richard Stallman <rms@gnu.org>]

    I don't know about the *Warning* buffer (I don't think I've ever even seen
    it), but in the case of comint:

     (1) If you use `comint-truncate-buffer' (in comint-output-filter-functions)
	 to keep comint buffers from getting too big (and in many cases it's a
	 very good idea), a line gets deleted at the beginning of the buffer for
	 every new line that gets inserted at the end, which can use massive
	 amounts of space in the undo list.

Perhaps `comint-truncate-buffer' should discard its own undo entries.
It could use `inhibit-undo', if we add such a feature.
Alternatively we could add a feature which says, "discard this undo entry,
and fix up the older entries so that they still work."  That could
be written in Lisp.