add verbose option to show hidden args

pkg/dev_compiler/lib/src/compiler/command.dart

Index: pkg/dev_compiler/lib/src/compiler/command.dart
diff --git a/pkg/dev_compiler/lib/src/compiler/command.dart b/pkg/dev_compiler/lib/src/compiler/command.dart
index 878070fbc1efc8077740289bfe36eee8422c9cc2..0b8a45b07aa5aaf8dff6030b54e3eda8efdc7dd3 100644
--- a/pkg/dev_compiler/lib/src/compiler/command.dart
+++ b/pkg/dev_compiler/lib/src/compiler/command.dart
@@ -14,22 +14,7 @@ import '../analyzer/context.dart' show AnalyzerOptions, parseDeclaredVariables;
 import 'compiler.dart' show BuildUnit, CompilerOptions, ModuleCompiler;
 import 'module_builder.dart';
 
-final ArgParser _argParser = () {
-  var argParser = new ArgParser(allowTrailingOptions: true)
-    ..addFlag('help', abbr: 'h', help: 'Display this message.')
-    ..addOption('out',
-        abbr: 'o', allowMultiple: true, help: 'Output file (required).')
-    ..addOption('module-root',
-        help: 'Root module directory.\n'
-            'Generated module paths are relative to this root.')
-    ..addOption('library-root',
-        help: 'Root of source files.\n'
-            'Generated library names are relative to this root.');
-  addModuleFormatOptions(argParser, allowMultiple: true);
-  AnalyzerOptions.addArguments(argParser);
-  CompilerOptions.addArguments(argParser);
-  return argParser;
-}();
+bool _verbose = false;
 
 /// Runs a single compile for dartdevc.
 ///
@@ -41,7 +26,8 @@ int compile(List<String> args, {void printFn(Object obj)}) {
   ArgResults argResults;
   var declaredVars = <String, String>{};
   try {
-    argResults = _argParser.parse(parseDeclaredVariables(args, declaredVars));
+    argResults = _argParser().parse(parseDeclaredVariables(args, declaredVars));
+    _verbose = argResults['verbose'];
   } on FormatException catch (error) {
     printFn('$error\n\n$_usageMessage');
     return 64;
@@ -80,6 +66,28 @@ $stackTrace
   }
 }
 
+ArgParser _argParser({bool hide: true}) {
+  var argParser = new ArgParser(allowTrailingOptions: true)
+    ..addFlag('help',
+        abbr: 'h',
+        help: 'Display this message.\n'
+            'Add --verbose to show hidden options.',
+        negatable: false)
+    ..addFlag('verbose', abbr: 'v', help: 'Verbose output.')
+    ..addOption('out',
+        abbr: 'o', allowMultiple: true, help: 'Output file (required).')
+    ..addOption('module-root',
+        help: 'Root module directory.\n'
+            'Generated module paths are relative to this root.')
+    ..addOption('library-root',
+        help: 'Root of source files.\n'
+            'Generated library names are relative to this root.');
+  addModuleFormatOptions(argParser, allowMultiple: true, hide: hide);
+  AnalyzerOptions.addArguments(argParser, hide: hide);
+  CompilerOptions.addArguments(argParser, hide: hide);
+  return argParser;
+}
+
 bool _changed(List<int> list1, List<int> list2) {
   var length = list1.length;
   if (length != list2.length) return true;
@@ -198,9 +206,9 @@ String _moduleForLibrary(
   return null; // unreachable
 }
 
-final _usageMessage =
+String get _usageMessage =>
     'Dart Development Compiler compiles Dart into a JavaScript module.'
-    '\n\n${_argParser.usage}';
+        '\n\n${_argParser(hide: !_verbose).usage}';
 
 void _usageException(String message) {
   throw new UsageException(message, _usageMessage);