diff -r 0b61d21f05cc -r ae20f52437e9 mercurial/help/internals/wireprotocolv2.txt
--- a/mercurial/help/internals/wireprotocolv2.txt	Thu Aug 30 17:43:47 2018 -0700
+++ b/mercurial/help/internals/wireprotocolv2.txt	Mon Sep 17 09:49:28 2018 -0700
@@ -82,6 +82,11 @@
    An array of bytestrings defining the supported framing protocol
    media types. Servers will not accept media types not in this list.
 
+pathfilterprefixes
+   (set of bytestring) Matcher prefixes that are recognized when performing
+   path filtering. Specifying a path filter whose type/prefix does not
+   match one in this set will likely be rejected by the server.
+
 rawrepoformats
    An array of storage formats the repository is using. This set of
    requirements can be used to determine whether a client can read a