First pass at build dependency graph for barback.

sdk/lib/_internal/pub/bin/pub.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 'dart:io';
 import 'dart:math' as math;
 
 import 'package:args/args.dart';
 import 'package:pathos/path.dart' as path;
@@ skipping 55 matching lines @@
       if (options['verbose']) {
         log.showAll();
       } else {
         log.showNormal();
       }
       break;
   }
 
   log.fine('Pub ${sdk.version}');
 
-  var cacheDir;
-  if (Platform.environment.containsKey('PUB_CACHE')) {
-    cacheDir = Platform.environment['PUB_CACHE'];
-  } else if (Platform.operatingSystem == 'windows') {
-    var appData = Platform.environment['APPDATA'];
-    cacheDir = path.join(appData, 'Pub', 'Cache');
-  } else {
-    cacheDir = '${Platform.environment['HOME']}/.pub-cache';
-  }
-
   validatePlatform().then((_) {
-    PubCommand.commands[options.command.name].run(cacheDir, options);
+    PubCommand.commands[options.command.name].run(options);
   });
 }
 
 ArgParser initArgParser() {
   var argParser = new ArgParser();
 
   // Add the global options.
   argParser.addFlag('help', abbr: 'h', negatable: false,
       help: 'Print this usage information.');
   argParser.addFlag('version', negatable: false,
@@ skipping 63 matching lines @@
   for (var name in names) {
     buffer.write('  ${padRight(name, length)}   '
         '${PubCommand.commands[name].description}\n');
   }
 
   buffer.write('\n');
   buffer.write(
       'Use "pub help [command]" for more information about a command.');
   log.message(buffer.toString());
 }