$ git clone -n https://src.fedoraproject.org/rpms/f27-backgrounds.git /var/lib/mock/f45-build-8584-391/root/chroot_tmpdir/scmroot/f27-backgrounds
Cloning into '/var/lib/mock/f45-build-8584-391/root/chroot_tmpdir/scmroot/f27-backgrounds'...
$ git fetch origin 1c022303415654ab00f660cf9a1ca1502555a4d9:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/f27-backgrounds
 * [new ref]         1c022303415654ab00f660cf9a1ca1502555a4d9 -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at 1c02230 Rebuilt for https://fedoraproject.org/wiki/Fedora_45_Mass_Rebuild