Ignore hidden options when calculating usage columns.

pkg/args/lib/src/usage.dart

 // Copyright (c) 2013, 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 args.src.usage;
 
 import 'dart:math';
 
 import '../args.dart';
 
@@ skipping 109 matching lines @@
   }
 
   String getAllowedTitle(String allowed) {
     return '      [$allowed]';
   }
 
   void calculateColumnWidths() {
     int abbr = 0;
     int title = 0;
     args.options.forEach((name, option) {
+      if (option.hide) return;
+
       // Make room in the first column if there are abbreviations.
       abbr = max(abbr, getAbbreviation(option).length);
 
       // Make room for the option.
       title = max(title, getLongOption(option).length);
 
       // Make room for the allowed help.
       if (option.allowedHelp != null) {
         for (var allowed in option.allowedHelp.keys) {
           title = max(title, getAllowedTitle(allowed).length);
@@ skipping 91 matching lines @@
 String padRight(String source, int length) {
   final result = new StringBuffer();
   result.write(source);
 
   while (result.length < length) {
     result.write(' ');
   }
 
   return result.toString();
 }