add 'debugrebuildstate' to rebuild the dirstate from a given revision
- added and removed files will be lost while recreating the dirstate
- modifications are not lost
1:3aa14bbc23d90:8633637036c13aa14bbc23d9 tip8633637036c18633637036c1+8633637036c13aa14bbc23d9 tipmerging file13aa14bbc23d9 tip3aa14bbc23d9 tip3aa14bbc23d9 tip3aa14bbc23d9 tip