DOC: wrong source docs corrected

procedures/entityVersioning.sql

@@ -245,8 +245,8 @@ CREATE FUNCTION db_2_0._get_head_iversion(
 RETURNS INT UNSIGNED
 READS SQL DATA
 BEGIN
-    -- This implementation assumes that the distance from the head equals the
-    -- difference between the _iversion numbers. This will not be correct anymore
+    -- This implementation assumes that the history is linear and the highest
+    -- _iversion number is always the head. This will not be correct anymore
     -- as soon as branches may split and merge. Then, a walk over the primary
     -- parents (_ipparent) will be necessary.
     RETURN (