CHelpCommand

public function getHelp()
{
    return parent::getHelp().' [command-name]';
}

public function run($args)
{
    $runner=$this->getCommandRunner();
    $commands=$runner->commands;
    if(isset($args[0]))
        $name=strtolower($args[0]);
    if(!isset($args[0]) || !isset($commands[$name]))
    {
        if(!empty($commands))
        {
            echo "Yii command runner (based on Yii v".Yii::getVersion().")\n";
            echo "Usage: ".$runner->getScriptName()." <command-name> [parameters...]\n";
            echo "\nThe following commands are available:\n";
            $commandNames=array_keys($commands);
            sort($commandNames);
            echo ' - '.implode("\n - ",$commandNames);
            echo "\n\nTo see individual command help, use the following:\n";
            echo "   ".$runner->getScriptName()." help <command-name>\n";
        }
        else
        {
            echo "No available commands.\n";
            echo "Please define them under the following directory:\n";
            echo "\t".Yii::app()->getCommandPath()."\n";
        }
    }
    else
        echo $runner->createCommand($name)->getHelp();
    return 1;
}