Re: "No further undo information" clutters *Messages* buffer

["Richard M. Stallman" <rms@gnu.org>]

    Eventually

    Undo!
    undo-more: No further undo information

    occupied more than 90% of my `*Messages*' buffer which made it quite
    difficult to trace more interesting error messages.

How did that happen?  From one sequence of undos, you'll only
get one such message.  So you must have done lots of sequences
of undos, and in each one, continued until you got an error.
It's not impossible, but it is strange and probably unusual.

Can you show us a complete, precise test case?

    Ideally, I wanted `undo' issue `Undo...', `Redo...', etc. first.  If the
    operation succeeded it would display `Undo...done', `Redo...done', etc.
    Otherwise, it would issue `Undo...', `Redo...', etc. with the according
    error text appended.  In any case `message_log_check_duplicate' would
    take care of the rest.

It already combines duplicate Undo! messages, so that you end up
with at most one of them from any sequence of undos.