First check in for pub package manager.

utils/pub/pub.dart

+// Copyright (c) 2012, 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.
+
+/**
+ * The main entrypoint for the pub command line application.
+ */
+#library('pub');
+
+#import('utils.dart');
+
+List<String, PubCommand> commands;
+
+main() {
+  final args = new Options().arguments;
+
+  // TODO(rnystrom): In addition to explicit "help" and "version" commands,
+  // should also add special-case support for --help and --version arguments to
+  // be consistent with other Unix apps.
+  commands = {
+    'version': new PubCommand('print Pub version', showVersion)
+  };
+
+  if (args.length == 0) {
+    showUsage();
+    return;
+  }
+
+  // Select the command.
+  final command = commands[args[0]];
+  if (command == null) {
+    print('Unknown command "${args[0]}".');
+    print('Run "pub help" to see available commands.');
+    exit(64); // see http://www.freebsd.org/cgi/man.cgi?query=sysexits.
+    return;
+  }
+
+  args.removeRange(0, 1);
+  command.function(args);
+}
+
+/** Displays usage information for the app. */
+void showUsage() {
+  print('Pub is a package manager for Dart.');
+  print('');
+  print('Usage:');
+  print('');
+  print('  pub command [arguments]');
+  print('');
+  print('The commands are:');
+  print('');
+
+  // Show the commands sorted.
+  // TODO(rnystrom): A sorted map would be nice.
+  int length = 0;
+  final names = <String>[];
+  for (final command in commands.getKeys()) {
+    length = Math.max(length, command.length);
+    names.add(command);
+  }
+
+  names.sort((a, b) => a.compareTo(b));
+
+  for (final name in names) {
+    print('  ${padRight(name, length)}   ${commands[name].description}');
+  }
+
+  print('');
+  print('Use "pub help [command]" for more information about a command.');
+}
+
+/** Displays pub version information. */
+void showVersion(List<String> args) {
+  // TODO(rnystrom): Store some place central.
+  print('Pub 0.0.0');
+}
+
+typedef void CommandFunction(List<String> args);
+
+class PubCommand {
+  final String description;
+  final CommandFunction function;
+
+  PubCommand(this.description, this.function);
+}