Re: *vc-diff* keeps undo information

[Richard Stallman]

    > Furthermore, it doesn't allow users to undo manual edits made
    > afterwards, e.g. splitting hunks, which is surely unacceptable.

    I agree, this is unacceptable.  Editing the diff output is useful for e.g.
    preparing the patches for sending by mail after manual editing, etc.

That is a good point.  So the thing to do is turn off undo
temporarily while the diff is being received, then turn it on
with an empty undo list.