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<PubCommand> commands;

[nweiz, 2012/03/30 00:38:37]

This should probably be a hash.

[Bob Nystrom, 2012/03/30 01:06:17]

Done.

+
+main() {
+  final args = new Options().arguments;
+
+  commands = [
+    new PubCommand('version', 'print Pub version', showVersion)

[nweiz, 2012/03/30 00:38:37]

Not something worth changing in this CL, but at some point it would be nice to
support --version, --help, and -h as well. Those are flags that I feel should be
supported by every command-line executable, regardless of its normal argument
conventions, because they're going to be used by users who haven't familiarized
themselves with the conventions yet.

[Bob Nystrom, 2012/03/30 01:06:17]

Good call. Added a TODO.

+  ];
+
+  if (args.length == 0) {
+    showUsage();
+    return;
+  }
+
+  // Select the command.
+  final commandName = args[0];
+  args.removeRange(0, 1);
+
+  for (final command in commands) {
+    if (command.name == commandName) {
+      command.function(args);
+      return;
+    }
+  }
+
+  // If we got here, the command wasn't recognized.
+  print('Unknown command "$commandName".');
+  print('Run "pub help" to see available commands.');
+  exit(64); // EX_USAGE, see http://www.freebsd.org/cgi/man.cgi?query=sysexits.
+}
+
+/** 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('');
+
+  int length = 0;
+  commands.forEach((command) => length = Math.max(length, command.name.length));
+
+  for (final command in commands) {
+    print('  ${padRight(command.name, length)}  ${command.description}');

[nweiz, 2012/03/30 00:38:37]

I'm not sure two spaces between the command name and the description is enough.
I found the example output a little tough to read. Git uses three, for
reference.

[Bob Nystrom, 2012/03/30 01:06:17]

Done.

+  }
+
+  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 name;
+  final String description;
+  final CommandFunction function;
+
+  PubCommand(this.name, this.description, this.function);
+}