Example:

We're working happily in a versioned bugdir, and our RCS knows who we
are.  We create a temporary repository copy from a previous revision
for diff generation.  We set the RCS for the copy to "None", since we
didn't bother initializing our normal RCS in the snapshot copy.  But
now the BugDir instantized on the copy doesn't know who we are!

Solution:

Track user id in the bugdir settings file.  If you
bugdir.settings["user_id"], it will be saved and loaded.  When loaded,
it will also set bugdir.user_id.  If you set rcs.user_id, it will be
returned by rcs.get_user_id(), instead of returing the output of
rcs._rcs_get_user_id().  We should be caching the output of
_rcs_get_user_id() anyway.