Hide lists in todo.txt file from other applications

plugins/todo-txt/gtd-provider-todo-txt.c

@@ -147,7 +147,7 @@ update_source (GtdProviderTodoTxt *self)
       color = gtd_task_list_get_color (list);
       color_str = gdk_rgba_to_string (color);
 
-      g_string_append_printf (contents, "@%s color:%s\n",
+      g_string_append_printf (contents, "h:1 @%s color:%s\n",
                               gtd_task_list_get_name (list),
                               color_str);