public History history(List<Build> builds) {
   List items = nu.nu(List.class);
   int size = builds.size();
   int limit = Math.min(size, runs);
   for (int i = 0; i < limit; i++) {
     Build build = builds.get(i);
     history(items, build);
   }
   return nu.nu(History.class, items);
 }
 private Id id(Build build) {
   DateTime date = build.getBuildDate();
   String label = "" + date.getMillis();
   return nu.nu(Id.class, label);
 }
 private Run run(Build build) {
   Id id = id(build);
   Result result = result(build);
   TimePoint timestamp = timestamp(build);
   return nu.nu(Run.class, id, result, timestamp);
 }