diff -r 15ce78517d4b -r 1d1d0914cb76 mercurial/cmdutil.py
--- a/mercurial/cmdutil.py	Thu Oct 01 19:16:00 2015 -0700
+++ b/mercurial/cmdutil.py	Thu Oct 01 20:21:16 2015 -0700
@@ -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