Appending working for library_list.json

pkg/docgen/bin/docgen.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:io';
 
 import 'package:args/args.dart';
 import 'package:logging/logging.dart';
 
 import '../lib/docgen.dart';
@@ skipping 31 matching lines @@
           logger.info(USAGE);
           exit(0);
         }
       });
   parser.addFlag('verbose', abbr: 'v', 
       help: 'Output more logging information.', negatable: false, 
       callback: (verbose) {
         if (verbose) Logger.root.level = Level.FINEST;
       });
   parser.addFlag('json', abbr: 'j', 
-      help: 'Outputs to JSON. Files are outputted to YAML by default.', 
+      help: 'Outputs to JSON. Files are outputted to YAML by default. ' 
+        'If --append is used, it takes the file-format of the previous '
+        'run stated in library_list.json ignoring the flag.', 
       negatable: true);
   parser.addFlag('include-private', 
       help: 'Flag to include private declarations.', negatable: false);
   parser.addFlag('include-sdk', 
       help: 'Flag to parse SDK Library files.', negatable: false);
   parser.addFlag('parse-sdk', 
       help: 'Parses the SDK libraries only.', 
       defaultsTo: false, negatable: false);
   parser.addOption('package-root', 
       help: 'Sets the package root of the library being analyzed.');
   parser.addFlag('append', 
-      help: 'Append to the docs folder, library_list.txt and index.txt', 
+      help: 'Append to the docs folder, library_list.json and index.txt', 
       defaultsTo: false, negatable: false);
   parser.addOption('introduction', 
       help: 'Adds the provided markdown text file as the introduction' 
         ' for the outputted documentation.', defaultsTo: '');
   
   return parser;
 }