started on git-annex-shell cluster support

Works down to P2P protocol.

The question now is, how to handle protocol version negotiation for
clusters? Connecting to each node to find their protocol versions and
using the lowest would be too expensive with a lot of nodes. So it seems
that the cluster needs to pick its own protocol version to use with the
client.

Then it can either negotiate that same version with the nodes when
it comes time to use them, or it can translate between multiple protocol
versions. That seems complicated. Thinking it would be ok to refuse to
use a node if it is not able to negotiate the same protocol version with
it as with the client. That will mean that sometimes need nodes to be
upgraded when upgrading the cluster's proxy. But protocol versions
rarely change.

P2P/Proxy.hs

@@ -12,7 +12,6 @@ module P2P.Proxy where
 import Annex.Common
 import P2P.Protocol
 import P2P.IO
-import qualified Remote
 import Utility.Metered (nullMeterUpdate)
 
 import Control.Concurrent.STM
@@ -60,20 +59,20 @@ type ProtoErrorHandled r =
  - brought up yet.
  -}
 getClientProtocolVersion 
-	:: Remote
+	:: UUID
 	-> ClientSide
 	-> (Maybe (ProtocolVersion, Maybe Message) -> Annex r)
 	-> ProtoErrorHandled r
-getClientProtocolVersion remote (ClientSide clientrunst clientconn) cont protoerrhandler =
-	protoerrhandler cont $ client $ getClientProtocolVersion' remote
+getClientProtocolVersion remoteuuid (ClientSide clientrunst clientconn) cont protoerrhandler =
+	protoerrhandler cont $ client $ getClientProtocolVersion' remoteuuid
   where
 	client = liftIO . runNetProto clientrunst clientconn
 
 getClientProtocolVersion'
-	:: Remote
+	:: UUID
 	-> Proto (Maybe (ProtocolVersion, Maybe Message))
-getClientProtocolVersion' remote = do
-	net $ sendMessage (AUTH_SUCCESS (Remote.uuid remote))
+getClientProtocolVersion' remoteuuid = do
+	net $ sendMessage (AUTH_SUCCESS remoteuuid)
 	msg <- net receiveMessage
 	case msg of
 		Nothing -> return Nothing