add special boolean option support

Author: Mizunashi Mana

lib/commands.js

@@ -29,7 +29,10 @@ function help(commands) {
             if (after.length > 0) after = "("+after.join("; ")+")";
             else after = "";
 
-            indent_output(2, '--' + option.name, option.description + ' ' + after);
+            var optname = '--';
+            if (typeof option.defaults === 'boolean') optname += '[no-]';
+            optname += option.name;
+            indent_output(2, optname, option.description + ' ' + after);
         });
         console.log('');
     });