Updates:
Labels: -Patch-countdown Patch-new
Comment #5 on issue 2874 by d...@gnu.org: Patch: Provide an \undo function
for turning overrides and sets into reverts and unsets
http://code.google.com/p/lilypond/issues/detail?id=2874#c5
\undo\hideNotes is equivalent to \unHideNotes, \undo\easyHeadsOn to
\easyHeadsOff. While this can't undo reverts, it is useful for a lot
of overriding commands defined in ly/property-init.ly, and is also
useful in combination with \hide/\omit.
http://codereview.appspot.com/6588067
