locking: take the `wlock` for the full `hg add` duration
Otherwise, there is a race condition window between the time we resolve the
file to add with the matcher and the time we lock the repo and modify the
dirstate.
For example, the working copy might have been updated away, or purged, and the
matched files would no longer be correct.
import pkgutil
__path__ = pkgutil.extend_path(__path__, __name__)