add single-map option

src/main.rs

@@ -57,6 +57,9 @@ struct Args {
 
    #[arg(long)]
    cutoff: Option<i32>,
+
+   #[arg(long,require_equals=true,num_args=0..=1,default_missing_value_os="true")]
+   single_map: Option<bool>,
 }
 
 #[test]