$ git clone -n https://src.fedoraproject.org/rpms/gstreamer1-plugins-ugly-free.git /var/lib/mock/f42-build-side-1-3583520-46889/root/chroot_tmpdir/scmroot/gstreamer1-plugins-ugly-free
Cloning into '/var/lib/mock/f42-build-side-1-3583520-46889/root/chroot_tmpdir/scmroot/gstreamer1-plugins-ugly-free'...
$ git fetch origin 8c8084510eb03a73e6dd65b91450e0d139bec3ee:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/gstreamer1-plugins-ugly-free
 * [new ref]         8c8084510eb03a73e6dd65b91450e0d139bec3ee -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at 8c80845 1.26.3