$ git clone -n https://src.fedoraproject.org/rpms/rubygem-rspec-core.git /var/lib/mock/f45-build-35275-694/root/chroot_tmpdir/scmroot/rubygem-rspec-core
Cloning into '/var/lib/mock/f45-build-35275-694/root/chroot_tmpdir/scmroot/rubygem-rspec-core'...
$ git fetch origin 19a2318b6ef7a3cfae7780a977321120dc829bb5:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/rubygem-rspec-core
 * [new ref]         19a2318b6ef7a3cfae7780a977321120dc829bb5 -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at 19a2318 Rebuilt for https://fedoraproject.org/wiki/Fedora_45_Mass_Rebuild