Refactor command code and add support for --help and --version.

utils/pub/command_list.dart

Index: utils/pub/command_list.dart
diff --git a/utils/pub/command_list.dart b/utils/pub/command_list.dart
index 973a4dedc48a7e41a72d928afbab7f4b578eed99..5079c9632223aaafe441e130fc3c3206c5c10950 100644
--- a/utils/pub/command_list.dart
+++ b/utils/pub/command_list.dart
@@ -3,13 +3,14 @@
 // BSD-style license that can be found in the LICENSE file.
 
 /** Handles the `list` pub command. */
-void commandList(PubOptions options, List<String> args) {
-  // TODO(rnystrom): Validate args. Right now, this just lists the packages in
-  // your cache.
-  final cache = new PackageCache(options.cacheDir);
-  cache.listAll().then((packages) {
-    for (final package in packages) {
-      print(package.name);
-    }
-  });
-}
+class ListCommand extends PubCommand {
+  String get description() => 'print the contents of repositories';

[nweiz, 2012/04/25 20:49:41]

This isn't really accurate... currently what this does is prints the contents of
the cache.

I'm not sure that's actually the most useful behavior, though. The cache should
be largely transparent to the user. It may make sense as an option, but it seems
like a more useful default would be to print the transitive dependency list of
the current package.

[Bob Nystrom, 2012/04/25 22:56:40]

Right.
Yeah, this command basically exists so that we can get some information out of
pub for some of the early integration tests. If you'd like, we can give it a
more obvious temp name like "debuglist". It's basically here so that I could
write tests of the basic package loading code before any other useful commands
had been written.

[nweiz, 2012/04/25 23:09:22]

Oh, sure. Maybe just add a comment about that here.

[Bob Nystrom, 2012/04/26 00:22:13]

Done.

+
+  void onRun() {
+    cache.listAll().then((packages) {
+      for (final package in packages) {
+        print(package.name);
+      }
+    });
+  }
+}