set analysis server exitCode on invalid cmdline arguments

pkg/analysis_server/lib/http_server.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.
 
 library http.server;
 
 import 'dart:io';
 
 import 'package:analysis_server/src/analysis_server.dart';
 import 'package:analysis_server/src/channel.dart';
@@ skipping 56 matching lines @@
 
     ArgResults results = parser.parse(args);
     if (results[HELP_OPTION]) {
       _printUsage(parser);
       return;
     }
     if (results[PORT_OPTION] == null) {
       print('Missing required port number');
       print('');
       _printUsage(parser);
+      exitCode = 1;
       return;
     }
 
     try {
       int port = int.parse(results[PORT_OPTION]);
       HttpServer.bind(InternetAddress.LOOPBACK_IP_V4, port).then(_handleServer);
       print('Listening on port $port');
     } on FormatException {
       print('Invalid port number: ${results[PORT_OPTION]}');
       print('');
       _printUsage(parser);
+      exitCode = 1;
       return;
     }
   }
 
   /**
    * Attach a listener to a newly created HTTP server.
    */
   void _handleServer(HttpServer server) {
     server.listen((HttpRequest request) {
       List<String> updateValues = request.headers[HttpHeaders.UPGRADE];
@@ skipping 74 matching lines @@
    * server.
    */
   void _returnUnknownRequest(HttpRequest request) {
     HttpResponse response = request.response;
     response.statusCode = HttpStatus.NOT_FOUND;
     response.headers.add(HttpHeaders.CONTENT_TYPE, "text/plain");
     response.write('Not found');
     response.close();
   }
 }