clean up fold, hashsum, kill

src/uu/fold/src/fold.rs

@@ -98,7 +98,7 @@ pub fn uumain(args: impl uucore::Args) -> i32 {
 fn handle_obsolete(args: &[String]) -> (Vec<String>, Option<String>) {
     for (i, arg) in args.iter().enumerate() {
         let slice = &arg;
-        if slice.starts_with('-') && slice.len() > 1 && slice.chars().nth(1).unwrap().is_digit(10) {
+        if slice.starts_with('-') && slice.chars().nth(1).map_or(false, |c| c.is_digit(10)) {
             let mut v = args.to_vec();
             v.remove(i);
             return (v, Some(slice[1..].to_owned()));

src/uu/hashsum/src/hashsum.rs

@@ -255,10 +255,8 @@ fn detect_algo<'a>(
                     }
                 }
             }
-            if alg.is_none() {
+            let alg = alg.unwrap_or_else(|| crash!(1, "You must specify hash algorithm!"));
-                crash!(1, "You must specify hash algorithm!")
+            (name, alg, output_bits)
-            };
-            (name, alg.unwrap(), output_bits)
         }
     }
 }

src/uu/kill/src/kill.rs

@@ -111,7 +111,7 @@ fn handle_obsolete(mut args: Vec<String>) -> (Vec<String>, Option<String>) {
     while i < args.len() {
         // this is safe because slice is valid when it is referenced
         let slice = &args[i].clone();
-        if slice.starts_with('-') && slice.len() > 1 && slice.chars().nth(1).unwrap().is_digit(10) {
+        if slice.starts_with('-') && slice.chars().nth(1).map_or(false, |c| c.is_digit(10)) {
             let val = &slice[1..];
             match val.parse() {
                 Ok(num) => {