protected function setAliases(array $routes)
    {
        foreach ($routes as $command => $route) {

            if (!isset($route['alias'])) {
                continue;
            }

            if (isset($this->aliases[$route['alias']])) {
                throw new OverflowException("Command alias '{$route['alias']}' is not unique");
            }

            $this->aliases[$route['alias']] = $command;
        }
    }