upgrade to edition 2021, clippy fixes, error fixed

src/main.rs

@@ -3,12 +3,13 @@ mod controllers;
 
 use std::process::exit;
 
-use exitcode;
-
 use controllers::{Controller, LinController, LogController, RawController};
 
+use crate::cli::build_cli;
+
 fn main() {
-    let matches = cli::parse_args();
+    let app = build_cli();
+    let matches = app.get_matches();
 
     let (default_ctrl, ctrls) = controllers::get_controllers();
 
@@ -41,7 +42,7 @@ fn main() {
     } else if matches.is_present("ful") {
         controller.set_brightness(controller.get_max_brightness());
     } else {
-        panic!("{}", ERROR_MSG);
+        build_cli().print_long_help().unwrap();
     }
 
     exit(exitcode::OK);