$ git clone -n https://src.fedoraproject.org/rpms/f45-backgrounds.git /var/lib/mock/f45-build-8627-392/root/chroot_tmpdir/scmroot/f45-backgrounds
Cloning into '/var/lib/mock/f45-build-8627-392/root/chroot_tmpdir/scmroot/f45-backgrounds'...
$ git fetch origin 13bb946090657ed26701f994d1583b4c03114dd6:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/f45-backgrounds
 * [new ref]         13bb946090657ed26701f994d1583b4c03114dd6 -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at 13bb946 Update to upstream 45.0.3