$ git clone -n https://src.fedoraproject.org/rpms/f43-backgrounds.git /var/lib/mock/f45-build-8617-392/root/chroot_tmpdir/scmroot/f43-backgrounds
Cloning into '/var/lib/mock/f45-build-8617-392/root/chroot_tmpdir/scmroot/f43-backgrounds'...
$ git fetch origin f9361075f40dc22e3494bde0b668e06102746b01:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/f43-backgrounds
 * [new ref]         f9361075f40dc22e3494bde0b668e06102746b01 -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at f936107 Rebuilt for https://fedoraproject.org/wiki/Fedora_45_Mass_Rebuild