$ git clone -n https://src.fedoraproject.org/rpms/polly.git /var/lib/mock/f42-build-864929-172657/root/chroot_tmpdir/scmroot/polly
Cloning into '/var/lib/mock/f42-build-864929-172657/root/chroot_tmpdir/scmroot/polly'...
$ git fetch origin b18d342101553b1703abaa7f4c71de3dacf9ffa3:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/polly
 * [new ref]         b18d342101553b1703abaa7f4c71de3dacf9ffa3 -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at b18d342 Update to 19.1.6