Interpret '%%' as literal '%' in format

docs/dunst.pod

@@ -324,6 +324,8 @@ equivalent notification attribute.
 
 =item B<%n>  progress value without any extra characters
 
+=item B<%%>  Literal %
+
 =back
 
 If any of these exists in the format but hasn't been specified in the

dunstrc

@@ -123,6 +123,7 @@
     #   %I  iconname (without its path)
     #   %p  progress value if set ([  0%] to [100%]) or nothing
     #   %n  progress value if set without any extra characters
+    #   %%  Literal %
     # Markup is allowed
     format = "<b>%s</b>\n%b"
 

src/notification.c

@@ -387,6 +387,13 @@ int notification_init(notification *n, int id)
                                                 n->progress ? pg : "",
                                                 MARKUP_NO);
                                 break;
+                        case '%':
+                                n->msg = notification_replace_single_field(
+                                                n->msg,
+                                                &substr,
+                                                "%",
+                                                MARKUP_NO);
+                                break;
                         case '\0':
                                 fprintf(stderr, "WARNING: format_string has trailing %% character."
                                                 "To escape it use %%%%.");