$ git clone -n https://src.fedoraproject.org/rpms/rubygem-spring.git /var/lib/mock/f45-build-35335-694/root/chroot_tmpdir/scmroot/rubygem-spring
Cloning into '/var/lib/mock/f45-build-35335-694/root/chroot_tmpdir/scmroot/rubygem-spring'...
$ git fetch origin cebd96ca4648d657b5c240632fc18edf18e86461:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/rubygem-spring
 * [new ref]         cebd96ca4648d657b5c240632fc18edf18e86461 -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at cebd96c Rebuilt for https://fedoraproject.org/wiki/Fedora_45_Mass_Rebuild