$ git clone -n https://src.fedoraproject.org/rpms/rubygem-rr.git /var/lib/mock/f45-build-35217-694/root/chroot_tmpdir/scmroot/rubygem-rr
Cloning into '/var/lib/mock/f45-build-35217-694/root/chroot_tmpdir/scmroot/rubygem-rr'...
$ git fetch origin a8ed6f4ed1903c42e4aa22ff1bc6719031ce5985:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/rubygem-rr
 * [new ref]         a8ed6f4ed1903c42e4aa22ff1bc6719031ce5985 -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at a8ed6f4 Rebuilt for https://fedoraproject.org/wiki/Fedora_45_Mass_Rebuild