add flutter channel command (#5561)

* add flutter channel command
fixes https://github.com/flutter/flutter/issues/2513

* fix test

* address comments

* remove unused imports

* fix lints

packages/flutter_tools/lib/executable.dart

@@ -14,6 +14,7 @@ import 'src/base/process.dart';
 import 'src/base/utils.dart';
 import 'src/commands/analyze.dart';
 import 'src/commands/build.dart';
+import 'src/commands/channel.dart';
 import 'src/commands/config.dart';
 import 'src/commands/create.dart';
 import 'src/commands/daemon.dart';
@@ -57,6 +58,7 @@ Future<Null> main(List<String> args) async {
   FlutterCommandRunner runner = new FlutterCommandRunner(verboseHelp: verboseHelp)
     ..addCommand(new AnalyzeCommand())
     ..addCommand(new BuildCommand())
+    ..addCommand(new ChannelCommand())
     ..addCommand(new ConfigCommand())
     ..addCommand(new CreateCommand())
     ..addCommand(new DaemonCommand(hidden: !verboseHelp))

packages/flutter_tools/lib/src/commands/channel.dart

+// Copyright 2015 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+import 'dart:async';
+
+import '../base/process.dart';
+import '../cache.dart';
+import '../globals.dart';
+import '../runner/flutter_command.dart';
+
+class ChannelCommand extends FlutterCommand {
+  @override
+  final String name = 'channel';
+
+  @override
+  final String description = 'List or switch flutter channels.';
+
+  @override
+  String get invocation => '${runner.executableName} $name [<channel-name>]';
+
+  @override
+  bool get requiresProjectRoot => false;
+
+  @override
+  Future<int> runInProject() async {
+    switch (argResults.rest.length) {
+      case 0:
+        return await _listChannels();
+      case 1:
+        return await _switchChannel(argResults.rest[0]);
+      default:
+        printStatus('Too many arguments.');
+        printStatus(usage);
+        return 2;
+    }
+  }
+
+  Future<int> _listChannels() async {
+    String currentBranch = runSync(
+        <String>['git', 'rev-parse', '--abbrev-ref', 'HEAD'],
+        workingDirectory: Cache.flutterRoot);
+
+    printStatus('Flutter channels:');
+    return runCommandAndStreamOutput(
+      <String>['git', 'branch', '-r'],
+      workingDirectory: Cache.flutterRoot,
+      mapFunction: (String line) {
+        List<String> split = line.split('/');
+        if (split.length < 2) return null;
+        String branchName = split[1];
+        if (branchName.startsWith('HEAD')) return null;
+        if (branchName == currentBranch) return '* $branchName';
+        return '  $branchName';
+      },
+    );
+  }
+
+  Future<int> _switchChannel(String branchName) {
+    printStatus('Switching to flutter channel named $branchName');
+    return runCommandAndStreamOutput(
+      <String>['git', 'checkout', branchName],
+      workingDirectory: Cache.flutterRoot,
+    );
+  }
+}

packages/flutter_tools/test/all.dart

@@ -17,6 +17,7 @@ import 'android_device_test.dart' as android_device_test;
 import 'android_sdk_test.dart' as android_sdk_test;
 import 'application_package_test.dart' as application_package_test;
 import 'base_utils_test.dart' as base_utils_test;
+import 'channel_test.dart' as channel_test;
 import 'config_test.dart' as config_test;
 import 'context_test.dart' as context_test;
 import 'create_test.dart' as create_test;
@@ -48,6 +49,7 @@ void main() {
   android_sdk_test.main();
   application_package_test.main();
   base_utils_test.main();
+  channel_test.main();
   config_test.main();
   context_test.main();
   create_test.main();

packages/flutter_tools/test/channel_test.dart

+// Copyright 2015 The Chromium Authors. 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/command_runner.dart';
+import 'package:flutter_tools/src/base/context.dart';
+import 'package:flutter_tools/src/base/logger.dart';
+import 'package:flutter_tools/src/commands/channel.dart';
+import 'package:test/test.dart';
+
+import 'src/common.dart';
+import 'src/context.dart';
+
+void main() {
+  group('channel', () {
+    testUsingContext('list', () async {
+      ChannelCommand command = new ChannelCommand();
+      CommandRunner runner = createTestCommandRunner(command);
+      expect(await runner.run(<String>['channel']), 0);
+      BufferLogger logger = context[Logger];
+      expect(logger.errorText, hasLength(0));
+      expect(logger.statusText, contains('channels'));
+      expect(logger.statusText, contains('master'));
+      // fails on bots
+      //expect(logger.statusText, contains('* ')); // current channel mark
+    });
+  });
+}