Add a [hide] argument to [ArgParser.addFlag].

pkg/args/test/usage_test.dart

Index: pkg/args/test/usage_test.dart
diff --git a/pkg/args/test/usage_test.dart b/pkg/args/test/usage_test.dart
index 27b038946ba912911fface2f0288fab911527cfa..f24b872a3cecf0c7de239b6ab8eb3985cfb3fc92 100644
--- a/pkg/args/test/usage_test.dart
+++ b/pkg/args/test/usage_test.dart
@@ -168,7 +168,7 @@ main() {
           ''');
     });
 
-    test("hidden flags don't appear in the help", () {
+    test("hidden options don't appear in the help", () {
       var parser = new ArgParser();
       parser.addOption('first', help: 'The first option');
       parser.addOption('second', hide: true);
@@ -181,6 +181,20 @@ main() {
           --third     The third option
           ''');
     });
+
+    test("hidden flags don't appear in the help", () {
+      var parser = new ArgParser();
+      parser.addFlag('first', help: 'The first flag');
+      parser.addFlag('second', hide: true);
+      parser.addFlag('third', help: 'The third flag');
+
+
+      validateUsage(parser,
+          '''
+          --[no-]first     The first flag
+          --[no-]third     The third flag
+          ''');
+    });
   });
 }