$ git clone -n https://src.fedoraproject.org/rpms/f26-backgrounds.git /var/lib/mock/f40-build-2686939-68076/root/chroot_tmpdir/scmroot/f26-backgrounds
Cloning into '/var/lib/mock/f40-build-2686939-68076/root/chroot_tmpdir/scmroot/f26-backgrounds'...
$ git fetch origin cc7c4419e88b8b9170ecb01d9fd19af9082d20c8:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/f26-backgrounds
 * [new ref]         cc7c4419e88b8b9170ecb01d9fd19af9082d20c8 -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at cc7c441 Rebuilt for https://fedoraproject.org/wiki/Fedora_40_Mass_Rebuild