feature: tag tests; choose tags on command line

lib/src/utils.dart

Index: lib/src/utils.dart
diff --git a/lib/src/utils.dart b/lib/src/utils.dart
index 7793d3084deaa94f9493ecd1f7b64039ea32b181..4516351a9bbe2bf943a8d4b512363611ed8a3d90 100644
--- a/lib/src/utils.dart
+++ b/lib/src/utils.dart
@@ -189,6 +189,19 @@ Map mergeMaps(Map map1, Map map2) {
   return result;
 }
 
+/// Returns a new list with all elements in both [list1] and [list2].
+///
+/// If an element exists in both lists, it is listed only once in the result.
+List mergeLists(List list1, List list2) {
+  var result = []..addAll(list1);
+  list2.forEach((element) {
+    if (!result.contains(element)) {
+      result.add(element);
+    }
+  });
+  return result;
+}
+
 /// Returns a sink that maps events sent to [original] using [fn].
 StreamSink mapSink(StreamSink original, fn(event)) {
   var controller = new StreamController(sync: true);
@@ -403,3 +416,9 @@ shelf.Middleware nestingMiddleware(String beneath) {
     return pathHandler.handler;
   };
 }
+
+/// Returns `true` iff [a] and [b] are both not null and share at least one
+/// element.
+bool intersect(Iterable a, Iterable b) {
+  return a != null && b != null && a.any(b.contains);
+}