$ git clone -n https://src.fedoraproject.org/rpms/rubygem-red-colors.git /var/lib/mock/f40-build-2639298-66352/root/chroot_tmpdir/scmroot/rubygem-red-colors
Cloning into '/var/lib/mock/f40-build-2639298-66352/root/chroot_tmpdir/scmroot/rubygem-red-colors'...
$ git fetch origin 3bdab5ee7bfd150ff8006c4e28d702b0cc42d72a:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/rubygem-red-colors
 * [new ref]         3bdab5ee7bfd150ff8006c4e28d702b0cc42d72a -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at 3bdab5e 0.4.0