$ git clone -n https://src.fedoraproject.org/rpms/gnutls.git /var/lib/mock/f40-build-797127-141067/root/chroot_tmpdir/scmroot/gnutls
Cloning into '/var/lib/mock/f40-build-797127-141067/root/chroot_tmpdir/scmroot/gnutls'...
$ git fetch origin c5694f3e42480aa013664046cad30ba402d227e1:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/gnutls
 * [new ref]         c5694f3e42480aa013664046cad30ba402d227e1 -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at c5694f3 Update keyring