$ git clone -n https://src.fedoraproject.org/rpms/rubygem-yard.git /var/lib/mock/f40-build-2639419-66359/root/chroot_tmpdir/scmroot/rubygem-yard
Cloning into '/var/lib/mock/f40-build-2639419-66359/root/chroot_tmpdir/scmroot/rubygem-yard'...
$ git fetch origin 5200db538521b1cf41aefad1555d0faaae4f55a7:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/rubygem-yard
 * [new ref]         5200db538521b1cf41aefad1555d0faaae4f55a7 -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at 5200db5 0.9.36