$ git clone -n https://src.fedoraproject.org/rpms/rubygem-generator_spec.git /var/lib/mock/f40-build-2413295-60564/root/chroot_tmpdir/scmroot/rubygem-generator_spec
Cloning into '/var/lib/mock/f40-build-2413295-60564/root/chroot_tmpdir/scmroot/rubygem-generator_spec'...
$ git fetch origin 2189e363864bb1a157265e1728112b04b9be0205:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/rubygem-generator_spec
 * [new ref]         2189e363864bb1a157265e1728112b04b9be0205 -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at 2189e36 update to 0.10.0