xpath BUGFIX special top-level paths
Tests included.
diff --git a/src/tree_data.h b/src/tree_data.h
index dcadc9d..3aa5ab9 100644
--- a/src/tree_data.h
+++ b/src/tree_data.h
@@ -1060,6 +1060,9 @@
/**
* @brief Search in the given data for instances of nodes matching the provided XPath.
*
+ * The expected format of the expression is JSON (::LYD_JSON) meaning the first node in every path
+ * must have its module name as prefix or be the special `*` value for all the nodes.
+ *
* If a list instance is being selected with all its key values specified (but not necessarily ordered)
* in the form `list[key1='val1'][key2='val2'][key3='val3']` or a leaf-list instance in the form
* `leaf-list[.='val']`, these instances are found using hashes with constant (*O(1)*) complexity