$ git clone -n https://github.com/xcp-ng-rpms/python3.git /var/lib/mock/v8.3-incoming-9101-27939/root/chroot_tmpdir/scmroot/python3
Cloning into '/var/lib/mock/v8.3-incoming-9101-27939/root/chroot_tmpdir/scmroot/python3'...
$ git fetch origin 7ceaa25eb61bdf253d0d3f4cc8f7b878e363cc6c:KOJI_FETCH_HEAD
From https://github.com/xcp-ng-rpms/python3
 * [new ref]         7ceaa25eb61bdf253d0d3f4cc8f7b878e363cc6c -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at 7ceaa25 Import python3-3.6.8-20.xs8.src.rpm