$ git clone -n https://src.fedoraproject.org/rpms/rubygem-open4.git /var/lib/mock/f45-build-35103-693/root/chroot_tmpdir/scmroot/rubygem-open4
Cloning into '/var/lib/mock/f45-build-35103-693/root/chroot_tmpdir/scmroot/rubygem-open4'...
$ git fetch origin 164956efa8fc8e1d8800001a5484d82c4aec7b7b:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/rubygem-open4
 * [new ref]         164956efa8fc8e1d8800001a5484d82c4aec7b7b -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at 164956e Rebuilt for https://fedoraproject.org/wiki/Fedora_45_Mass_Rebuild