I've always been quite fond of the way that gnus labelled parts in MIME
messages. Here's a start at doing the same for notmuch.el. Is this
something that might be accepted upstream if I continue?

Obvious next steps are:
        - allow the user to choose which parts have buttons (i.e perhaps
          not text/plain by default),
        - have the inserted buttons actually do something useful (toggle
          visibility and/or save).

dme.
-- 
David Edmondson, http://dme.org