#2 Revision history needs to be modifyable.

[Mitch Denny]

If people are going to be setting up canned
presentations in CheckPoint it would assist them by
being able to delete a particular version of a file (or an
entire branch) so that it no longer exists.

This has a few subtle implications on how CheckPoint
would need to be implemented. First, we would probably
have to keep complete copies of files, not progressive
diffs - or just hide the diffs which could get pretty
complex pretty fast.