refactor man and completion with clap derive api

src/config/args.rs

@@ -6,16 +6,21 @@ const ARG_CONFIG: &str = "config";
 
 /// Represents the config file path argument. This argument allows the
 /// user to customize the config file path.
-pub fn arg() -> Arg {
-    Arg::new(ARG_CONFIG)
-        .help("Set a custom configuration file path")
+pub fn global_args() -> impl IntoIterator<Item = Arg> {
+    [Arg::new(ARG_CONFIG)
+        .help("Override the configuration file path")
+        .long_help(
+            "Override the configuration file path
+
+If the file under the given path does not exist, the wizard will propose to create it.",
+        )
         .long("config")
         .short('c')
         .global(true)
-        .value_name("PATH")
+        .value_name("path")]
 }
 
 /// Represents the config file path argument parser.
-pub fn parse_arg(matches: &ArgMatches) -> Option<&str> {
+pub fn parse_global_arg(matches: &ArgMatches) -> Option<&str> {
     matches.get_one::<String>(ARG_CONFIG).map(String::as_str)
 }