diff -r 0b7475ea38cf -r 6847542bb8d7 mercurial/help/internals/wireprotocol.txt
--- a/mercurial/help/internals/wireprotocol.txt	Wed Mar 28 14:55:13 2018 -0700
+++ b/mercurial/help/internals/wireprotocol.txt	Wed Mar 28 15:44:47 2018 -0700
@@ -1686,3 +1686,19 @@
 changesets satisfied the request.
 
 TODO consider exposing phase of heads in response
+
+known
+-----
+
+Determine whether a series of changeset nodes is known to the server.
+
+The command accepts the following arguments:
+
+nodes
+   (array of bytestrings) List of changeset nodes whose presence to
+   query.
+
+The response is a bytestring where each byte contains a 0 or 1 for the
+corresponding requested node at the same index.
+
+TODO use a bit array for even more compact response