2 questions about undo-list

[Andreas Politz]

Hello !

1. I want to transparently remove whitespace
from the end of the lines before saving a buffer.
By `transparently' I mean without it disturbing
the undo mechanism.

I tried
(let (buffer-undo-list)
     (replace-regexp ...))

in a before-save-hook, but it _does_ mess up the
undo history. How should I do this ? (Too much to ask ?)

2. self-insert-commands enter the undo-list in packs a 20
chars or so (=> (info "(elisp)Undo") ). Is this kind of
grouping possible for other commands as well ? Kind of
like the opposite of undo-boundary.

Thanks,

-ap