Re: New undo element (fun . args)

[Richard Stallman]

    1) it does not work with the "undo-in-region" funtionality.

Yes, that is true.  However, to make this work required more
than just adding a range to the undo element.  It also
has to say the size change it makes within that region.
undo-elt-in-region and undo-delta have to handle it.
And the code in undo-make-selective-list has to be updated
to modify these elements for other elements that get skipped.

    2) AFAICS, it effectively blocks any future extensions to the
       undo list format.

Not really, but there's no need to argue about it.

I think this format is best:

   (apply DELTA BEG END FUN . ARGS)

It should be documented that BEG and END should be the