Stefan Monnier <monnier@IRO.UMontreal.CA> writes:

>> 1) undo-auto--undoably-changed-buffers becomes an alist
>
>>  ((0 . (buffers*))
>>   (1 . (buffers*))
>>   (2 . (buffers*)))
>
>> where the key is the return of (recursion-depth)
>
>> 2) undo-auto--boundaries operates only on buffers at the
>> current-recursion-depth. Or, probably, at the current of greater
>> recursion depth, to ensure that undo-buffers happens when a recursive
>> edit exits.
>
> Hmm... sounds pretty good, and I think you can do it more simply:
> just let-bind undo-auto--undoably-changed-buffers to nil when entering
> a recursive edit.

Tried it before I got your mail. Seems to function.

Simple let binding would not give quite the same functionality, because
of the last part -- I also add a boundary to buffers with a greater
recursive depth; with a let binding, I think these would be unbound for
commands that lower the recursion depth.