Don't truncate multi-line command descriptions.

lib/command_runner.dart

 // Copyright (c) 2014, 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 'dart:collection';
 import 'dart:math' as math;
 
 import 'src/arg_parser.dart';
 import 'src/arg_results.dart';
@@ skipping 353 matching lines @@
   var visible = names.where((name) => !commands[name].hidden);
   if (visible.isNotEmpty) names = visible;
 
   // Show the commands alphabetically.
   names = names.toList()..sort();
   var length = names.map((name) => name.length).reduce(math.max);
 
   var buffer =
       new StringBuffer('Available ${isSubcommand ? "sub" : ""}commands:');
   for (var name in names) {
+    var lines = commands[name].description.split("\n");
     buffer.writeln();
-    buffer.write('  ${padRight(name, length)}   '
-        '${commands[name].description.split("\n").first}');
+    buffer.write('  ${padRight(name, length)}   ${lines.first}');
+
+    for (var line in lines.skip(1)) {
+      buffer.writeln();
+      buffer.write(' ' * (length + 5));
+      buffer.write(line);
+    }
   }
 
   return buffer.toString();
 }