refactoring: move ls builtin line formatting

src/builtins/ls.rs

@@ -37,16 +37,18 @@ impl Builtin for Ls {
                 file_type = "link"
             }
             println!(
-                "{:} | {:4} | {}",
-                right_padding(&file_name, 16),
-                file_type,
-                metadata.len()
+                "{}",
+                format_line(&right_padding(&file_name, 16), file_type, metadata.len())
             )
         }
         Ok(())
     }
 }
 
+fn format_line(right_padding: &str, file_type: &str, file_size: u64) -> String {
+    format!("{:} | {:4} | {}", right_padding, file_type, file_size)
+}
+
 fn right_padding(s: &str, max: usize) -> String {
     let mut tmp = String::from_str(s).unwrap();
     for _ in tmp.len()..max {