🚀 go-pugleaf

>> It could be useful if it were possible to have several undo lists for
>> a single buffer, kept independantly for some specified regions.
>
>In Zmacs, if the region is set, undo limits its actions to those fully
>contained within the region.  If an action spread across the boundary of the
>region, it failed.  This was a staggering win.

This would be a really great feature.  Unfortunately, in order to make
this work, the positions in the undo list would have to become markers
instead of plain integers, you'd end up with *lots* of markers in your
buffer, and editing would slow down.  Zmacs kept the buffer as a
linked list of lines and markers stuck with their lines, so each
marker moved around a lot less often, and neat tricks like the
restricted undo and intervals were easier.

It might be possible to build restricted undo on top of the interval
code, if Emacs 19 acquires this feature.

-JimB