Re: Undo discard prompt

[Richard Stallman]

    Well I didn't say "routinely": it happened 4 times until now.
    And I don't think they were the result of a bug.  They mostly (3 times)
    occured because I did something like:
    1 - copy a large file (or a buffer).
    2 - work on the copy by removing most of its content.

I can see why #2 could put a lot of information in the undo list.  But
why would this make the undo list for one single command very large?

    The remaing case occured in conjunction with the command
    diff-context->unified on a large patch file.  Maybe the command shouldn't
    keep the undo info, but find that I do undo this command.

It makes sense for this command to be undoable.  Indeed, for a big
enough file, it would trigger this question.

I wonder if the command is written in a way that produces
unnecessarily large bulk of undo info.  Perhaps some simple changes
would reduce the size of its undo info by a factor of 2.
This, combined with increasing the default value of undo-outer-limit,
would make such questions very rare.