util: add `nb_bytes` argument to `copyfile` to partially copy a file
When set, this allow to copy only the first `nb_bytes` of a file. This will be
useful for censor/strip operation with revlogv2.
Differential Revision: https://phab.mercurial-scm.org/D10798
# name space package to host third party extensions
from __future__ import absolute_import
import pkgutil
__path__ = pkgutil.extend_path(__path__, __name__)