$ git clone -n https://src.fedoraproject.org/rpms/rubygem-unf_ext.git /var/lib/mock/f45-build-35424-695/root/chroot_tmpdir/scmroot/rubygem-unf_ext
Cloning into '/var/lib/mock/f45-build-35424-695/root/chroot_tmpdir/scmroot/rubygem-unf_ext'...
$ git fetch origin 67ec4b0a750f722de0b7ea657046c1be980ffd41:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/rubygem-unf_ext
 * [new ref]         67ec4b0a750f722de0b7ea657046c1be980ffd41 -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at 67ec4b0 Rebuilt for https://fedoraproject.org/wiki/Fedora_45_Mass_Rebuild