$ git clone -n https://src.fedoraproject.org/rpms/gnutls.git /var/lib/mock/f42-build-3460218-45515/root/chroot_tmpdir/scmroot/gnutls
Cloning into '/var/lib/mock/f42-build-3460218-45515/root/chroot_tmpdir/scmroot/gnutls'...
$ git fetch origin 63494651c6d5db52377755e7af9c2639c3edf1c4:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/gnutls
 * [new ref]         63494651c6d5db52377755e7af9c2639c3edf1c4 -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at 6349465 Rebuild GnuTLS