use clap; // 2.33.0
use clap::{App, Arg, ArgMatches};

pub struct UI;
impl UI {
    pub fn populate_cli_args(app: clap::App<'static, 'static>) -> clap::App<'static, 'static> {
        app.arg(
            Arg::with_name("config")
            .short("c")
            .long("config")
            .value_name("FILE")
            .help("Sets a custom config file")
            .takes_value(true)
        )
    }
}

pub struct FileHandler;
impl FileHandler {
    pub fn populate_cli_args(app: clap::App<'static, 'static>) -> clap::App<'static, 'static> {
        app.arg(
            Arg::with_name("config")
            .short("c")
            .long("config")
            .value_name("FILE")
            .help("Sets a custom config file")
            .takes_value(true)
        )
    }
}

fn main() {
    let mut app = clap::App::new("My super program");

    app = UI::populate_cli_args(app);
    app = FileHandler::populate_cli_args(app);
    let matches = app.get_matches();
}