Re-add --kill flag for compatibility

--kill translates to --signal SIGKILL

src/cli.rs

@@ -33,8 +33,7 @@ pub fn clear_screen() {
 #[allow(unknown_lints)]
 #[allow(or_fun_call)]
 pub fn get_args() -> Args {
-    let args =
-        App::new("watchexec")
+    let args = App::new("watchexec")
         .version(crate_version!())
         .about("Execute commands when watched files change")
         .arg(Arg::with_name("command")
@@ -68,6 +67,10 @@ pub fn get_args() -> Args {
                  .takes_value(true)
                  .number_of_values(1)
                  .value_name("signal"))
+        .arg(Arg::with_name("kill")
+                 .help("Send SIGKILL to child processes (deprecated, use -s SIGKILL instead)")
+                 .short("k")
+                 .long("kill"))
         .arg(Arg::with_name("debug")
                  .help("Print debugging messages to stderr")
                  .short("d")
@@ -102,9 +105,16 @@ pub fn get_args() -> Args {
         .arg(Arg::with_name("once").short("1").hidden(true))
         .get_matches();
 
-    let cmd = values_t!(args.values_of("command"), String).unwrap().join(" ");
+    let cmd = values_t!(args.values_of("command"), String)
+        .unwrap()
+        .join(" ");
     let paths = values_t!(args.values_of("path"), String).unwrap_or(vec![String::from(".")]);
-    let signal = args.value_of("signal").map(str::to_string); // Convert Option<&str> to Option<String>
+
+    // Treat --kill as --signal SIGKILL (for compatibility with older syntax)
+    let signal = match args.is_present("kill") {
+        true => Some("SIGKILL".to_string()),
+        false => args.value_of("signal").map(str::to_string), // Convert Option<&str> to Option<String>
+    };
 
     let mut filters = values_t!(args.values_of("filter"), String).unwrap_or(vec![]);
 
@@ -138,6 +148,12 @@ pub fn get_args() -> Args {
             .exit();
     }
 
+    if signal.is_some() && args.is_present("kill") {
+        // TODO: Error::argument_conflict() might be the better fit, usage was unclear, though
+        Error::value_validation_auto(format!("--kill and --signal is ambiguous.\n       Hint: Use only '--signal SIGKILL' without --kill"))
+            .exit();
+    }
+
     Args {
         cmd: cmd,
         paths: paths,