$ git clone -n https://src.fedoraproject.org/rpms/mock.git /var/lib/mock/f45-build-19012-539/root/chroot_tmpdir/scmroot/mock
Cloning into '/var/lib/mock/f45-build-19012-539/root/chroot_tmpdir/scmroot/mock'...
$ git fetch origin e89bde94eac6ef728514366d80c1124b56ca642c:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/mock
 * [new ref]         e89bde94eac6ef728514366d80c1124b56ca642c -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at e89bde9 Update mock to 6.9-1