Add an explicit distinction between a command's description and summary.

test/utils.dart

 // Copyright (c) 2013, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 import 'dart:async';
 
 import 'package:args/args.dart';
 import 'package:args/command_runner.dart';
 import 'package:test/test.dart';
 
@@ skipping 21 matching lines @@
 
   final name = "multiline";
   final description = "Multi\nline.";
   final takesArguments = false;
 
   void run() {
     hasRun = true;
   }
 }
 
+class MultilineSummaryCommand extends MultilineCommand {
+  String get summary => description;
+}
+
 class HiddenCommand extends Command {
   var hasRun = false;
 
   final name = "hidden";
   final description = "Set a value.";
   final hidden = true;
   final takesArguments = false;
 
   void run() {
     hasRun = true;
@@ skipping 32 matching lines @@
 }
 
 Matcher throwsUsageError(message, usage) {
   return throwsA(predicate((error) {
     expect(error, new isInstanceOf<UsageException>());
     expect(error.message, message);
     expect(error.usage, usage);
     return true;
   }));
 }