Add support for upper case in arguments.

tests/lib/args/args_test.dart

 // Copyright (c) 2012, 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_test');
 
 #import('../../../lib/unittest/unittest.dart');
 #import('../../../lib/args/args.dart');
 
 main() {
@@ skipping 389 matching lines @@
       test('stops parsing at "--"', () {
         var parser = new ArgParser();
         parser.addFlag('woof', defaultsTo: false);
         parser.addOption('meow', defaultsTo: 'kitty');
 
         var results = parser.parse(['--woof', '--', '--meow']);
         expect(results['woof'], isTrue);
         expect(results['meow'], equals('kitty'));
         expect(results.rest, orderedEquals(['--meow']));
       });
+
+      test('handles options with case-sensitivity', () {
+        var parser = new ArgParser();
+        parser.addFlag('recurse', defaultsTo: false, abbr:'R');
+        var results = parser.parse(['-R']);
+        expect(results['recurse'], isTrue);
+        expect(results.rest, [ ]);
+        throwsFormat(parser, ['-r']);
+      });
     });
   });
 
   group('ArgParser.getUsage()', () {
     test('negatable flags show "no-" in title', () {
       var parser = new ArgParser();
       parser.addFlag('mode', help: 'The mode');
 
       validateUsage(parser,
           '''
@@ skipping 200 matching lines @@
         throw new IllegalArgumentException(
             'Line "$line" does not have enough indentation.');
       }
 
       lines[i] = line.substring(indent);
     }
   }
 
   return Strings.join(lines, '\n');
 }