Early description of resync/resolve

The last thing resync does is move RESYNC -> RESOLVE .
The existence of a RESYNC directory means the resync
didn't get done or is in progress.  If in progress,
RESYNC/BitKeeper/tmp/pid should be the process id.

When resolve is done,

a) create a lock file in repository, fsync it
b) move old ChangeSet out of the way
c) move the new s.ChangeSet into place, fsync it
d) start moving the files into place
e) remove lock file and old ChangeSet