Re: undo in loaddefs.el buffer

[Richard Stallman]

    Moreover, in addition to those two and texinfo-format-buffer and
    loaddefs.el, there is a problem when you autorevert the Buffer Menu.
    At regular intervals, you get asked the "undo" question, even when the
    Buffer Menu is very tiny (like three buffers).

That suggests something is making too much undo info.  It would be
good to debug why it makes so much undo info.  Forcing Emacs into the
debugger when it is asking the question would be a way to do that.  Or
stopping Emacs with GDB.

    3.  Fail to put in undo boundaries, thus accumulating one huge single
        undo entry, eventually triggering the undo-outer-limit question.

    Situation 3 seems to happen rather easily with timers.

Maybe that means Emacs should put in undo boundaries at the
beginning and end of a timer.

    Although the problem with the buffer menu appears to be caused by (3)
    I believe that the reasons for discarding undo info when reverting a
    file, also apply to reverting the Buffer Menu.  So the patch below,
    discards all undo info when reverting the Buffer Menu.

I think that is right, and likewise for Dired.  Reverting
should clear out the undo info, since it is supposed to give
a clean slate.