+ *
+ * @returns
+ *
+ * NOTMUCH_STATUS_SUCCESS: excluded was added successfully.
+ *
+ * NOTMUCH_STATUS_XAPIAN_EXCEPTION: a Xapian exception occured.
+ * Most likely a problem lazily parsing the query string.
+ *
+ * NOTMUCH_STATUS_IGNORED: tag is explicitely present in the query, so
+ * not excluded.