dirname: accept repeated flag

src/uu/dirname/src/dirname.rs

@@ -64,6 +64,7 @@ pub fn uu_app() -> Command {
         .about(ABOUT)
         .version(crate_version!())
         .override_usage(format_usage(USAGE))
+        .args_override_self(true)
         .infer_long_args(true)
         .arg(
             Arg::new(options::ZERO)

tests/by-util/test_dirname.rs

@@ -40,6 +40,16 @@ fn test_path_without_trailing_slashes_and_zero() {
         .stdout_is("/root/alpha/beta/gamma/delta/epsilon\u{0}");
 }
 
+#[test]
+fn test_repeated_zero() {
+    new_ucmd!()
+        .arg("--zero")
+        .arg("--zero")
+        .arg("foo/bar")
+        .succeeds()
+        .stdout_only("foo\u{0}");
+}
+
 #[test]
 fn test_root() {
     new_ucmd!().arg("/").run().stdout_is("/\n");