Fix cut when lines dont end with specified delim (#5844)

Print lines without delimiters only when they end with specified line terminator('\n' by default or `\0` if `-s`)

Signed-off-by: Andrei Stan <[email protected]>
Co-authored-by: Sylvestre Ledru <[email protected]>

Author: andreistan26

src/uu/cut/src/cut.rs

@@ -213,11 +213,8 @@ fn cut_fields_implicit_out_delim<R: Read, M: Matcher>(
         let mut print_delim = false;
 
         if delim_search.peek().is_none() {
-            if !only_delimited {
+            if !only_delimited && line[line.len() - 1] == newline_char {
                 out.write_all(line)?;
-                if line[line.len() - 1] != newline_char {
-                    out.write_all(&[newline_char])?;
-                }
             }
 
             return Ok(true);

tests/by-util/test_cut.rs

@@ -282,6 +282,15 @@ fn test_multiple() {
     assert_eq!(result.stderr_str(), "");
 }
 
+#[test]
+fn test_newline_delimited() {
+    new_ucmd!()
+        .args(&["-f", "1", "-d", "\n"])
+        .pipe_in("a:1\nb:")
+        .succeeds()
+        .stdout_only_bytes("a:1\n");
+}
+
 #[test]
 fn test_multiple_mode_args() {
     for args in [