diff --git a/mercurial/cmdutil.py b/mercurial/cmdutil.py
index 15ce78517d4be9db88914209ea98e62d22ad32f3_bWVyY3VyaWFsL2NtZHV0aWwucHk=..1d1d0914cb761dcd1a41d1e163b2aec303d0e29b_bWVyY3VyaWFsL2NtZHV0aWwucHk= 100644
--- a/mercurial/cmdutil.py
+++ b/mercurial/cmdutil.py
@@ -3349,6 +3349,9 @@
         'hg bundle --type TYPE'.
 
     It accept format in the form [compression][-version]|[version]
+
+    Consensus about extensions of the format for various bundle2 feature
+    is to prefix any feature with "+". eg "+treemanifest" or "gzip+phases"
     """
     comp, version = None, None