feat: script and exec runtimes with configurable shell

Add runtime: script (shell file, default /bin/bash, optional stop_script) and runtime: exec (executable with args, optional stop_executable). Both support service_type simple|oneshot and working_dir.

systemd/generator.go

@@ -87,6 +87,15 @@ func ServiceName(u config.Unit, prefix, suffix string) string {
 
 // Generate produces the .service file content for a unit.
 func Generate(u config.Unit, prefix, suffix string) (string, error) {
+	if u.Command == "" {
+		if u.IsScript() && u.Script == "" {
+			return "", fmt.Errorf("unit %s: runtime script requires 'script' (or 'command')", u.Name)
+		}
+		if u.IsExec() && u.Executable == "" {
+			return "", fmt.Errorf("unit %s: runtime exec requires 'executable' (or 'command')", u.Name)
+		}
+	}
+
 	data := templateData{
 		ServiceName:    ServiceName(u, prefix, suffix),
 		Unit:           u,
@@ -96,6 +105,16 @@ func Generate(u config.Unit, prefix, suffix string) (string, error) {
 	}
 
 	switch {
+	case u.IsScript() && u.Command == "":
+		data.ExecStart, data.ExecStop = buildScriptCommands(u)
+		data.Label = filepath.Base(u.ShellPath()) + " script"
+		data.WorkingDir = u.WorkingDir
+		data.ServiceType = serviceType(u)
+	case u.IsExec() && u.Command == "":
+		data.ExecStart, data.ExecStop = buildExecutableCommands(u)
+		data.Label = "executable"
+		data.WorkingDir = u.WorkingDir
+		data.ServiceType = serviceType(u)
 	case u.IsStack() && u.Command == "" && StackMode(u) == StackModeCompose:
 		data.ExecStart, data.ExecStop = buildComposeCommands(u)
 		data.Label = "podman-compose stack"
@@ -134,6 +153,33 @@ func runtimeService(runtime string) string {
 	return ""
 }
 
+func serviceType(u config.Unit) string {
+	if u.ServiceType == "oneshot" {
+		return "oneshot"
+	}
+	return "simple"
+}
+
+func buildScriptCommands(u config.Unit) (start, stop string) {
+	shell := quoteArg(u.ShellPath())
+	start = shell + " " + quoteArg(u.Script)
+	if u.StopScript != "" {
+		stop = shell + " " + quoteArg(u.StopScript)
+	}
+	return start, stop
+}
+
+func buildExecutableCommands(u config.Unit) (start, stop string) {
+	parts := []string{quoteArg(u.Executable)}
+	for _, a := range u.Args {
+		parts = append(parts, quoteArg(a))
+	}
+	if u.StopExecutable != "" {
+		stop = quoteArg(u.StopExecutable)
+	}
+	return strings.Join(parts, " "), stop
+}
+
 func buildExecCommands(u config.Unit) (start, stop string) {
 	// If a custom command is provided, use it directly
 	if u.Command != "" {