$ git clone -n https://src.fedoraproject.org/rpms/python-BTrees.git /var/lib/mock/f41-build-813077-148555/root/chroot_tmpdir/scmroot/python-BTrees
Cloning into '/var/lib/mock/f41-build-813077-148555/root/chroot_tmpdir/scmroot/python-BTrees'...
$ git fetch origin b13e97f40b840a21efddfa3f9c1a25387eacb40d:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/python-BTrees
 * [new ref]         b13e97f40b840a21efddfa3f9c1a25387eacb40d -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at b13e97f Version 6.0