Support subcommands in pub and pub help.

sdk/lib/_internal/pub/lib/src/command/cache.dart

Index: sdk/lib/_internal/pub/lib/src/command/cache.dart
diff --git a/sdk/lib/_internal/pub/lib/src/command/cache.dart b/sdk/lib/_internal/pub/lib/src/command/cache.dart
index 97e5dbe7614ec99e4d209b792aab7b9eed431b82..dbef31531b5743f95a357e5e78e780f4870b3ac8 100644
--- a/sdk/lib/_internal/pub/lib/src/command/cache.dart
+++ b/sdk/lib/_internal/pub/lib/src/command/cache.dart
@@ -4,48 +4,15 @@
 
 library pub.command.cache;
 
-import 'dart:async';
-import 'dart:convert';
-
 import '../command.dart';
-import '../exit_codes.dart' as exit_codes;
-import '../io.dart';
-import '../log.dart' as log;
+import 'cache_list.dart';
 
 /// Handles the `cache` pub command.
 class CacheCommand extends PubCommand {
-  String get description => "Inspect the system cache.";
-  String get usage => "pub cache list";
-  bool get hidden => true;
-  bool get requiresEntrypoint => false;
-  bool get takesArguments => true;
-
-  Future onRun() {
-    // TODO(rnystrom): Use subcommand for "list".
-    if (commandOptions.rest.length != 1) {
-      log.error('The cache command expects one argument.');
-      this.printUsage();
-      return flushThenExit(exit_codes.USAGE);
-    }
-
-    if ((commandOptions.rest[0] != 'list')) {
-      log.error('Unknown cache command "${commandOptions.rest[0]}".');
-      this.printUsage();
-      return flushThenExit(exit_codes.USAGE);
-    }
-
-    // TODO(keertip): Add flag to list packages from non default sources
-    var packagesObj = <String, Map>{};
+  String get description => "Work with the system cache.";
+  String get usage => "pub cache <subcommand>";
 
-    for (var package in cache.sources.defaultSource.getCachedPackages()) {
-
-      var packageInfo = packagesObj.putIfAbsent(package.name, () => {});
-      packageInfo[package.version.toString()] = {'location': package.dir};
-    }
-
-    // TODO(keertip): Add support for non-JSON format
-    // and check for --format flag
-    log.message(JSON.encode({'packages': packagesObj}));
-  }
+  final subcommands = {
+    "list": new CacheListCommand()
+  };
 }
-