Get rid of all the library tags.

lib/src/command/downgrade.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.
 
-library pub.command.downgrade;
-
 import 'dart:async';
 
 import '../command.dart';
 import '../log.dart' as log;
 import '../solver/version_solver.dart';
 
 /// Handles the `downgrade` pub command.
 class DowngradeCommand extends PubCommand {
   String get name => "downgrade";
   String get description =>
@@ skipping 14 matching lines @@
   Future run() async {
     var dryRun = argResults['dry-run'];
     await entrypoint.acquireDependencies(SolveType.DOWNGRADE,
         useLatest: argResults.rest, dryRun: dryRun);
     if (isOffline) {
       log.warning("Warning: Downgrading when offline may not update you to "
           "the oldest versions of your dependencies.");
     }
   }
 }