Add thr:in-reply-to to ostatus representer.

lib/pleroma/web/ostatus/activity_representer.ex

@@ -1,4 +1,19 @@
 defmodule Pleroma.Web.OStatus.ActivityRepresenter do
+  alias Pleroma.Activity
+  require Logger
+
+  defp get_in_reply_to(%{"object" => %{ "inReplyTo" => in_reply_to}}) do
+    with %Activity{data: %{"id" => id}} <- Activity.get_create_activity_by_object_ap_id(in_reply_to) do
+      [{:"thr:in-reply-to", [ref: to_charlist(id)], []}]
+    else _e ->
+      Logger.debug("Couldn't find replied-to activity:")
+      Logger.debug(in_reply_to)
+      []
+    end
+  end
+
+  defp get_in_reply_to(_), do: []
+
   def to_simple_form(%{data: %{"object" => %{"type" => "Note"}}} = activity, user) do
     h = fn(str) -> [to_charlist(str)] end
 
@@ -12,6 +27,8 @@ defmodule Pleroma.Web.OStatus.ActivityRepresenter do
       {:link, [rel: 'enclosure', href: to_charlist(url["href"]), type: to_charlist(url["mediaType"])], []}
     end)
 
+    in_reply_to = get_in_reply_to(activity.data)
+
     [
       {:"activity:object-type", ['http://activitystrea.ms/schema/1.0/note']},
       {:"activity:verb", ['http://activitystrea.ms/schema/1.0/post']},
@@ -22,7 +39,7 @@ defmodule Pleroma.Web.OStatus.ActivityRepresenter do
       {:updated, h.(updated_at)},
       {:"ostatus:conversation", [], h.(activity.data["context"])},
       {:link, [href: h.(activity.data["context"]), rel: 'ostatus:conversation'], []}
-    ] ++ attachments
+    ] ++ attachments ++ in_reply_to
   end
 
   def to_simple_form(_,_), do: nil

lib/pleroma/web/ostatus/feed_representer.ex

@@ -16,6 +16,7 @@ defmodule Pleroma.Web.OStatus.FeedRepresenter do
     [{
       :feed, [
         xmlns: 'http://www.w3.org/2005/Atom',
+        "xmlns:thr": 'http://purl.org/syndication/thread/1.0',
         "xmlns:activity": 'http://activitystrea.ms/spec/1.0/',
         "xmlns:poco": 'http://portablecontacts.net/spec/1.0',
         "xmlns:ostatus": 'http://ostatus.org/schema/1.0'