Get loaded config file name

[Bouska]

For logging reasons, I want to retrieve the loaded config filename. One solution would been to have a access to the config_name_ variable but even then, if the default filename wasn't accessible, I wouldn't know (if the parameter config_required was not set).

Currently I have the following hack to get that information but it's pretty ugly:

    std::shared_ptr<CLI::App> _app = std::make_shared<CLI::App>("App");
    std::string _config_name = "./config.ini";
    _app->set_config("--config",
                   _config_name,
                   "Read a config file",
                   false);
    _config_name = (_app->get_option("--config")->results().empty())?_config_name:_app->get_option("--config")->results().at(0);
    std::ifstream test{_config_name};
    _config_name = (!test.good())?"None":_config_name;

It would be nice to have a nicer way to do that.