send a presence query when the buddy list is displayed

This ensures that clients that have not sent presence in a while will show
up in the list.

Assistant/Threads/XMPPClient.hs

@@ -88,8 +88,8 @@ xmppClientThread = NamedThread "XMPPClient" $ do
 relayNetMessage :: Assistant (XMPP ())
 relayNetMessage = convert <$> waitNetMessage
   where
-	convert (NotifyPush us) =
-		putStanza $ gitAnnexPresence $ encodePushNotification us
+	convert (NotifyPush us) = putStanza $ pushNotification us
+	convert QueryPresence = putStanza presenceQuery
 
 data DecodedStanza 
 	= PresenceMessage Presence

Assistant/Types/NetMessager.hs

@@ -13,7 +13,11 @@ import Control.Concurrent.STM
 import Control.Concurrent.MSampleVar
 
 {- Messages that can be sent out of band by a network messager. -}
-data NetMessage = NotifyPush [UUID]
+data NetMessage 
+	-- indicate that pushes have been made to the repos with these uuids
+	= NotifyPush [UUID]
+	-- requests other clients to inform us of their presence
+	| QueryPresence
 
 {- Controls for the XMPP client. 
  -

Assistant/WebApp/Configurators/Pairing.hs

@@ -31,6 +31,8 @@ import Annex.UUID
 #ifdef WITH_XMPP
 import Assistant.XMPP.Client
 import Network.Protocol.XMPP
+import Assistant.Types.NetMessager
+import Assistant.NetMessager
 #endif
 import Utility.UserInfo
 
@@ -55,6 +57,9 @@ getStartPairR = pairPage $ do
 #else
 	let localsupported = False
 #endif
+	{- Ask buddies to send presence info, to get the buddy list
+	 - populated. -}
+	lift $ liftAssistant $ sendNetMessage QueryPresence
 	$(widgetFile "configurators/pairing/start")
 #else
 #ifdef WITH_PAIRING

Assistant/XMPP.hs

@@ -84,6 +84,9 @@ decodePushNotification (Element name attrs _nodes)
 	fromContent (ContentText t) = t
 	fromContent (ContentEntity t) = t
 
+pushNotification :: [UUID] -> Presence
+pushNotification = gitAnnexPresence . encodePushNotification
+
 {- A request for other git-annex clients to send presence. -}
 presenceQuery :: Presence
 presenceQuery = gitAnnexPresence $ Element gitAnnexTagName