Port "Fix 3PID invite room state over federation" to dinsic

changelog.d/5464.bugfix

@@ -0,0 +1 @@
+Fix missing invite state after exchanging 3PID invites over federaton.

docker/README.md

@@ -14,7 +14,7 @@ This image is designed to run either with an automatically generated
 configuration file or with a custom configuration that requires manual editing.
 
 An easy way to make use of this image is via docker-compose. See the
-[contrib/docker](../contrib/docker) section of the synapse project for
+[contrib/docker](https://github.com/matrix-org/synapse/tree/master/contrib/docker) section of the synapse project for
 examples.
 
 ### Without Compose (harder)

synapse/handlers/federation.py

@@ -2613,12 +2613,6 @@ def on_exchange_third_party_invite_request(self, origin, room_id, event_dict):
         # though the sender isn't a local user.
         event.internal_metadata.send_on_behalf_of = get_domain_from_id(event.sender)
 
-        # XXX we send the invite here, but send_membership_event also sends it,
-        # so we end up making two requests. I think this is redundant.
-        returned_invite = yield self.send_invite(origin, event)
-        # TODO: Make sure the signatures actually are correct.
-        event.signatures.update(returned_invite.signatures)
-
         member_handler = self.hs.get_room_member_handler()
         yield member_handler.send_membership_event(None, event, context)