[ardour-dev] clarification on last CVS commit

[Paul Davis]

The work I did today on cleanup has a couple of important
effects. Most significantly, when you cleanup now, you will lose *all*
undo/redo history for the session. This is made clear in the GUI (a
confirmatory dialog pops up). This is because we have to clear out the
undo/redo history in order to get rid of audio files that are no
longer in current use, but references to them remain in some previous
state(s) of the session (a state reachable by undo/redo).

There were a couple of changes to playlist semantics that as far as I
can tell should have no side-effects. But given the history of such
claims in relation to ardour, caution is advised.

--p