munge.clj

(defn munge [vs]
  (if (== 1 (count (first vs)))
    (reduce into vs)
    (let [gs (group-by #(% 0) vs)]
      (map (fn [k v]
             {:data k :children v})
           (keys gs)
           (->> (vals gs)
                (map (partial map #(subvec % 1)))
                (map munge))))))

;;; or keyd by field value, without :data & :children

(defn munge [vs]
  (if (== 1 (count (first vs)))
    (reduce into vs)
    (let [gs (group-by #(% 0) vs)]
      (zipmap (keys gs)
              (->> (vals gs)
                   (map (partial map #(subvec % 1)))
                   (map munge))))))