$ git clone -n https://src.fedoraproject.org/rpms/rubygem-test-unit-ruby-core.git /var/lib/mock/f45-build-35384-695/root/chroot_tmpdir/scmroot/rubygem-test-unit-ruby-core
Cloning into '/var/lib/mock/f45-build-35384-695/root/chroot_tmpdir/scmroot/rubygem-test-unit-ruby-core'...
$ git fetch origin b3d11edddebbcc64631b2937a1628b61578f6497:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/rubygem-test-unit-ruby-core
 * [new ref]         b3d11edddebbcc64631b2937a1628b61578f6497 -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at b3d11ed 1.0.16