$ git clone -n https://src.fedoraproject.org/rpms/rubygem-optimist.git /var/lib/mock/f45-build-35043-693/root/chroot_tmpdir/scmroot/rubygem-optimist
Cloning into '/var/lib/mock/f45-build-35043-693/root/chroot_tmpdir/scmroot/rubygem-optimist'...
$ git fetch origin 18e92efc83715a234f0adf4ff5cceb278b4482af:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/rubygem-optimist
 * [new ref]         18e92efc83715a234f0adf4ff5cceb278b4482af -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at 18e92ef Rebuilt for https://fedoraproject.org/wiki/Fedora_45_Mass_Rebuild