$ git clone -n https://src.fedoraproject.org/rpms/rubygem-multi_json.git /var/lib/mock/f45-build-35045-693/root/chroot_tmpdir/scmroot/rubygem-multi_json
Cloning into '/var/lib/mock/f45-build-35045-693/root/chroot_tmpdir/scmroot/rubygem-multi_json'...
$ git fetch origin c9f394d5bb325d5d9c07f29bc746a25c5fccc967:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/rubygem-multi_json
 * [new ref]         c9f394d5bb325d5d9c07f29bc746a25c5fccc967 -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at c9f394d Rebuilt for https://fedoraproject.org/wiki/Fedora_45_Mass_Rebuild