fix -l and -L to be mutually exclusive so that last one wins (#30)

src/lib.rs

@@ -707,14 +707,16 @@ pub fn uu_app() -> Command {
                 .short('L')
                 .long("files-without-match")
                 .help("print only names of FILEs with no selected lines")
-                .action(ArgAction::SetTrue),
+                .action(ArgAction::SetTrue)
+                .overrides_with("files_with_matches"),
         )
         .arg(
             Arg::new("files_with_matches")
                 .short('l')
                 .long("files-with-matches")
                 .help("print only names of FILEs with selected lines")
-                .action(ArgAction::SetTrue),
+                .action(ArgAction::SetTrue)
+                .overrides_with("files_without_match"),
         )
         .arg(
             Arg::new("count")

tests/test_grep.rs

@@ -460,6 +460,25 @@ fn files_with_and_without_matches() {
         .stdout_only("many\n");
 }
 
+#[test]
+fn files_with_and_without_matches_mutually_exclusive() {
+    // Test that -l and -L are mutually exclusive with last-one-wins semantics
+    let (scene, mut c) = ucmd();
+    scene.fixtures.write("file", "match\n");
+
+    // -l -L: last flag (-L) wins, so no output (file has match, -L excludes it)
+    c.args(&["-l", "-L", "match", "file"])
+        .succeeds()
+        .stdout_only("");
+
+    // -L -l: last flag (-l) wins, so filename is printed
+    let (scene, mut c) = ucmd();
+    scene.fixtures.write("file", "match\n");
+    c.args(&["-L", "-l", "match", "file"])
+        .succeeds()
+        .stdout_only("file\n");
+}
+
 #[test]
 fn count_combined_with_listing_flags() {
     let (scene, _) = ucmd();