filelog.parsemeta() and filelog.packmeta() are used to decode
and encode metadata for file copies and censor.
An upcoming commit will move the core logic for censoring revlogs
into revlog.py. This would create a cycle between revlog.py and
filelog.py. So we move these metadata functions to revlog.py.
filelog.parsemeta() and filelog.packmeta() have been moved to the revlog module.