enforce strict service name rules

Signed-off-by: fbt <fbt@fleshless.org>

ssm

@@ -767,6 +767,11 @@ flag_edit_service && { edit; die $?; }
 service_name = "${1##*/}"
 readonly service_name
 
+# Enforce service_name to conform to BASH's name constraints
+[[ $service_name =~ ^[a-zA-Z_][a-zA-Z0-9_]+?$ ]] || {
+	die 77 "Invalid service name: '$service_name'"
+}
+
 # These depend on the service_name and make little sense to reconfigure.
 service_ready_flag := "$rundir/$service_name.ready"
 service_enabled_flag := "$rundir/$service_name.enabled"