First pass at build dependency graph for barback.

sdk/lib/_internal/pub/bin/pub.dart

Index: sdk/lib/_internal/pub/bin/pub.dart
diff --git a/sdk/lib/_internal/pub/bin/pub.dart b/sdk/lib/_internal/pub/bin/pub.dart
index 5c893e1d3e14e56ef0121575389d2dbf92343885..79711ddb280a9b7b58df97b92d3f38a2672d12f5 100644
--- a/sdk/lib/_internal/pub/bin/pub.dart
+++ b/sdk/lib/_internal/pub/bin/pub.dart
@@ -73,18 +73,8 @@ void main() {
 
   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);
   });
 }