[CLI] Support for CVS style command line

[John Keyes <jo...@integralsource.com>]

The CVS command line is defined as follows:

   cvs [options] command [command-options]

Ideally I would like to have CLI support this implicity, i.e.
validate the 'command' value (this was a feature already
recommended by Mike McLean and modified by Max Rydahl Andersen)
and based on this value parse the remaining Options.

There are two steps in this:
   . value validation
   . mapping value to Options

So here's an example:

   ValueValidator commandValidator = new StringValidator() {
       public boolean validate(String value) {
           ...
       }
   }

   OptionsMap optionsMap = new OptionsMap();
   optionsMap.add("checkout", checkoutOptions);
   optionsMap.add("co", checkoutOptions);

   // this means that there is an Anonymous Argument which will
   // have one value and the HelpFormatter will spit 'command'
   // out in the help text, the value found in the args will
   // be validated by the specified validator
   Argument command = abuilder.withOptionMap(optionsMap)
                              .withValidator(commandValidator)
                              .createAnonymous("command",1);

   // args - "cvs co file.txt"
   CommandLine line = parser.parse(opts, args);

The parse would find 'co' as the Anonymous Argument, and then
validate that the value is allowable, when it confirms that it
is valuable then query the OptionsMap to see if there are any
Options specified for that value.  If there are Options, then
parse the remaining args (file.txt) using them.  If there
are no Options, then throw an exception as there is only
one value allowed for the anonymous argument.

What do people think of this?  Does it sound good?  Are there
any better ideas?

Cheers,
-John K
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Jakarta Commons CLI
http://jakarta.apache.org/commons/cli

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