Eric Hopper <hopper@omnifarious.org> [Fri, 07 Oct 2005 10:48:27 -0700] rev 1457
This implements the nodesbetween method, and it removes the newer method
and replaces it with calls to nodesbetween.
nodesbetween calculates all the changesets needed to have a complete
revision graph between a given set of base nodes and a given set of
head nodes.