fix: add allow_hyphen_values to --with-nth

Matches --nth and --hide-nth behavior to support documented negative indices syntax.

src/options.rs

@@ -196,7 +196,13 @@ pub struct SkimOptions {
     /// See **nth** for the details
     #[cfg_attr(
         feature = "cli",
-        arg(long, default_value = "", help_heading = "Search", value_delimiter = ',')
+        arg(
+            long,
+            default_value = "",
+            help_heading = "Search",
+            value_delimiter = ',',
+            allow_hyphen_values = true,
+        )
     )]
     pub with_nth: Vec<String>,
 

src/options_tests.rs

@@ -2,6 +2,7 @@
 //! and history initialization, which apply defaults and cross-option rules.
 
 use super::*;
+use crate::field::FieldRange;
 use crate::item::RankCriteria;
 use crate::tui::statusline::InfoDisplay;
 
@@ -287,3 +288,38 @@ fn build_history_file_adds_history_keybindings() {
 
     let _ = std::fs::remove_file(&qpath);
 }
+
+/// Helper: parse real CLI args with no env influence.
+fn parse_args(args: &[&str]) -> Result<SkimOptions, clap::Error> {
+    SkimOptions::merge_args_and_parse(
+        "sk".to_string(),
+        None,
+        None,
+        args.iter().map(|s| (*s).to_string()),
+        None,
+    )
+}
+
+#[test]
+fn negative_field_indices_parse_for_every_nth_flag() {
+    // All three flags document the same `nth` syntax, which includes `-1` for the
+    // last field; a space-separated negative value must not be read as a flag.
+    for flag in ["--nth", "--with-nth", "--hide-nth"] {
+        let opts = parse_args(&[flag, "-1"]).unwrap_or_else(|e| panic!("{flag} -1 failed to parse: {e}"));
+        let got = match flag {
+            "--nth" => &opts.nth,
+            "--with-nth" => &opts.with_nth,
+            _ => &opts.hide_nth,
+        };
+        assert_eq!(got, &vec!["-1".to_string()], "{flag}");
+        assert_eq!(
+            FieldRange::from_str(&got[0]),
+            Some(FieldRange::Single(-1)),
+            "{flag} should resolve to the last field"
+        );
+    }
+
+    // ...and a negative index inside a comma-separated list.
+    let opts = parse_args(&["--with-nth", "2,-1"]).expect("--with-nth 2,-1 should parse");
+    assert_eq!(opts.with_nth, vec!["2".to_string(), "-1".to_string()]);
+}

tests/cli.rs

@@ -128,6 +128,19 @@ fn filter_mode_no_sort_preserves_input_order() {
     );
 }
 
+#[test]
+fn with_nth_accepts_space_separated_negative_index() {
+    // `--with-nth -1` (space form) used to be parsed as a missing value, while
+    // `--nth -1` and `--with-nth=-1` both worked.
+    let (code, stdout, stderr) = run_sk_argv("a b c", &["-f", "c", "--with-nth", "-1"], &[]);
+    assert_eq!(code, Some(0), "stderr: {stderr}");
+    assert_eq!(stdout.trim_end(), "a b c");
+
+    // The space form and the `=` form must agree.
+    let (code_eq, stdout_eq, _) = run_sk_argv("a b c", &["-f", "c", "--with-nth=-1"], &[]);
+    assert_eq!((code, stdout), (code_eq, stdout_eq));
+}
+
 #[test]
 fn select_1_with_output_format() {
     // --output-format renders the selected item through the printf branch.