improve flutter create error message (#6525)

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

@@ -47,13 +47,19 @@ class CreateCommand extends FlutterCommand {
   @override
   Future<int> runCommand() async {
     if (argResults.rest.isEmpty) {
-      printStatus('No option specified for the output directory.');
-      printStatus(usage);
+      printError('No option specified for the output directory.');
+      printError(usage);
       return 2;
     }
 
     if (argResults.rest.length > 1) {
-      printStatus('Multiple output directories specified.');
+      printError('Multiple output directories specified.');
+      for (String arg in argResults.rest) {
+        if (arg.startsWith('-')) {
+          printError('Try moving $arg to be immediately following $name');
+          break;
+        }
+      }
       return 2;
     }
 

packages/flutter_tools/test/create_test.dart

@@ -7,6 +7,7 @@ import 'dart:convert';
 import 'dart:io';
 
 import 'package:args/command_runner.dart';
+import 'package:flutter_tools/src/base/logger.dart';
 import 'package:flutter_tools/src/cache.dart';
 import 'package:flutter_tools/src/commands/create.dart';
 import 'package:flutter_tools/src/dart/sdk.dart';
@@ -82,6 +83,21 @@ void main() {
       expect(code, 0);
     });
 
+    // Verify that we help the user correct an option ordering issue
+    BufferLogger logger = new BufferLogger();
+    testUsingContext('produces sensible error message', () async {
+      Cache.flutterRoot = '../..';
+
+      CreateCommand command = new CreateCommand();
+      CommandRunner runner = createTestCommandRunner(command);
+
+      int code = await runner.run(<String>['create', temp.path, '--pub']);
+      expect(code, 2);
+      expect(logger.errorText, contains('Try moving --pub'));
+    }, overrides:  <Type, dynamic>{
+      Logger: logger,
+    });
+
     // Verify that we fail with an error code when the file exists.
     testUsingContext('fails when file exists', () async {
       Cache.flutterRoot = '../..';