Add summary command to bot.

tools/gardening/bin/summary.dart

+// Copyright (c) 2017, 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.
+
+import 'package:args/args.dart';
+import 'package:gardening/src/bot.dart';
+import 'package:gardening/src/util.dart';
+
+void help(ArgParser argParser) {
+  print('Summarizes the current status of the build bot.');
+  print('Usage: summary [options]');
+  print('  where options are:');
+  print(argParser.usage);
+}
+
+main(List<String> args) async {
+  ArgParser argParser = createArgParser();
+  ArgResults argResults = argParser.parse(args);
+  processArgResults(argResults);
+  var bot = new Bot(logdog: argResults['logdog']);
+  var recentUris = bot.mostRecentUris;
+  var results = await bot.readResults(recentUris);
+  results.forEach((result) {
+    if (result.hasFailures) {
+      print("${result.buildUri} has failures.");
+    }
+  });
+  bot.close();
+}