Basename arguments simple format (#3736)

* basename: support simple format

* tests/basename: add tests for simple format

* basename: follow clippy advice

src/uu/basename/src/basename.rs

@@ -31,6 +31,23 @@ pub fn uumain(args: impl uucore::Args) -> UResult<()> {
     let args = args
         .collect_str(InvalidEncodingHandling::ConvertLossy)
         .accept_any();
+
+    // Since options have to go before names,
+    // if the first argument is not an option, then there is no option,
+    // and that implies there is exactly one name (no option => no -a option),
+    // so simple format is used
+    if args.len() > 1 && !args[1].starts_with('-') {
+        if args.len() > 3 {
+            return Err(UUsageError::new(
+                1,
+                format!("extra operand {}", args[3].to_string().quote()),
+            ));
+        }
+        let suffix = if args.len() > 2 { args[2].as_ref() } else { "" };
+        println!("{}", basename(&args[1], suffix));
+        return Ok(());
+    }
+
     //
     // Argument parsing
     //

tests/by-util/test_basename.rs

@@ -174,3 +174,21 @@ fn test_triple_slash() {
     let expected = if cfg!(windows) { "\\\n" } else { "/\n" };
     new_ucmd!().arg("///").succeeds().stdout_is(expected);
 }
+
+#[test]
+fn test_simple_format() {
+    new_ucmd!().args(&["a-a", "-a"]).succeeds().stdout_is("a\n");
+    new_ucmd!()
+        .args(&["a--help", "--help"])
+        .succeeds()
+        .stdout_is("a\n");
+    new_ucmd!().args(&["a-h", "-h"]).succeeds().stdout_is("a\n");
+    new_ucmd!().args(&["f.s", ".s"]).succeeds().stdout_is("f\n");
+    new_ucmd!().args(&["a-s", "-s"]).succeeds().stdout_is("a\n");
+    new_ucmd!().args(&["a-z", "-z"]).succeeds().stdout_is("a\n");
+    new_ucmd!()
+        .args(&["a", "b", "c"])
+        .fails()
+        .code_is(1)
+        .stderr_contains("extra operand 'c'");
+}