Added the continueParsing option to ArgParser.

pkg/args/test/parse_test.dart

Index: pkg/args/test/parse_test.dart
diff --git a/pkg/args/test/parse_test.dart b/pkg/args/test/parse_test.dart
index 715c2269218537157fff9a758ef37005905de3cc..82f25c9db9c69f035f0af94e13833428a960d481 100644
--- a/pkg/args/test/parse_test.dart
+++ b/pkg/args/test/parse_test.dart
@@ -389,14 +389,62 @@ main() {
       test('stops parsing args when a non-option-like arg is encountered', () {
         var parser = new ArgParser();
         parser.addFlag('woof');
+        parser.addFlag('neigh');

[Bob Nystrom, 2013/04/22 22:59:03]

Why add neigh to this test?

         parser.addOption('meow');
         parser.addOption('tweet', defaultsTo: 'bird');
 
-        var results = parser.parse(['--woof', '--meow', 'v', 'not', 'option']);
+        var results = parser.parse(['--woof', '--meow', 'v', 'not', 'option',
+            '--tweet', 'devrel', '--neigh', 'end' ]);
         expect(results['woof'], isTrue);
+        expect(results['neigh'], isFalse);
         expect(results['meow'], equals('v'));
         expect(results['tweet'], equals('bird'));
-        expect(results.rest, orderedEquals(['not', 'option']));
+        expect(results.rest, orderedEquals(['not', 'option', '--tweet',
+            'devrel', '--neigh', 'end']));
+      });
+
+      test('with continueParsing, continues parsing when non-option-like'
+        ' arg is encountered', () {
+        var parser = new ArgParser();
+        parser.addFlag('woof');
+        parser.addFlag('neigh');
+        parser.addOption('meow');
+        parser.addOption('tweet', defaultsTo: 'bird');
+
+        var results = parser.parse(['--woof', '--meow', 'v', 'not', 'option',
+            '--tweet', 'devrel', '--neigh', 'end' ],

[Bob Nystrom, 2013/04/22 22:59:03]

This test is pretty complicated. How about simplifying it to just the one thing
being tested, like:

parser.addFlag('woof');

parser.parse(['notoption', 'woof']);

+            continueParsing: true);
+        expect(results['woof'], isTrue);
+        expect(results['neigh'], isTrue);
+        expect(results['meow'], equals('v'));
+        expect(results['tweet'], equals('devrel'));
+        expect(results.rest, orderedEquals(['not', 'option', 'end']));
+      });
+

[Bob Nystrom, 2013/04/22 22:59:03]

Add a test for what happens if continueParsing is true and an argument that
looks like an option but isn't ('--notopt') is encountered.

+      test('with continueParsing, gathers all seen arguments to leaf command',
+          () {
+        var parser = new ArgParser();
+        parser.addFlag('woof');
+        parser.addFlag('neigh');
+        parser.addOption('tweet', defaultsTo: 'bird');
+
+        var command = parser.addCommand('v');
+        command.addCommand('option')
+          ..addOption('tweet', defaultsTo: 'foo')
+          ..addFlag('neigh');

[Bob Nystrom, 2013/04/22 22:59:03]

We should use a consistent style here. How about just ditching the cascades?

+        command.addCommand('end');
+
+        var results = parser.parse(['--woof', 'meow', 'v', 'not', 'option',
+            '--tweet', 'devrel', '--neigh', 'end' ],
+            continueParsing: true);
+        expect(results['woof'], isTrue);
+        expect(results['tweet'], equals('bird'));
+        expect(results.rest, equals([]));
+        expect(results.command.name, equals('v'));
+        expect(results.command.rest, equals([]));
+        expect(results.command.command['neigh'], isTrue);
+        expect(results.command.command.name, equals('option'));
+        expect(results.command.command.rest, orderedEquals(['meow', 'not', 'end']));

[Bob Nystrom, 2013/04/22 22:59:03]

This test is big and hard to read. Split it into a couple of smaller ones:

1. Test that skipped arguments are passed to the leafmost command.
2. Test parsed options are given to the leafmost command when both a command and
its parent define the same option.

Also, I would move these tests to command_test.dart

       });
 
       test('stops parsing at "--"', () {