refactor ref change watching

Added to change notification to P2P protocol.

Switched to a TBChan so that a single long-running thread can be
started, and serve perhaps intermittent requests for change
notifications, without buffering all changes in memory.

The P2P runner currently starts up a new thread each times it waits
for a change, but that should allow later reusing a thread. Although
each connection from a peer will still need a new watcher thread to run.

The dependency on stm-chans is more or less free; some stuff in yesod
uses it, so it was already indirectly pulled in when building with the
webapp.

This commit was sponsored by Francois Marier on Patreon.

3 files changed, 6 insertions, 11 deletions

diff --git a/RemoteDaemon/Transport/Ssh.hs b/RemoteDaemon/Transport/Ssh.hs
index 205165062..59502f8d3 100644
--- a/RemoteDaemon/Transport/Ssh.hs
+++ b/RemoteDaemon/Transport/Ssh.hs
@@ -17,6 +17,7 @@ import Utility.SimpleProtocol
 import qualified Git
 import Git.Command
 import Utility.ThreadScheduler
+import Annex.ChangedRefs
 
 import Control.Concurrent.STM
 import Control.Concurrent.Async
@@ -73,7 +74,7 @@ transportUsingCmd' cmd params (RemoteRepo r _) url transporthandle ichan ochan =
 			Just SshRemote.READY -> do
 				send (CONNECTED url)
 				handlestdout fromh
-			Just (SshRemote.CHANGED shas) -> do
+			Just (SshRemote.CHANGED (ChangedRefs shas)) -> do
 				whenM (checkNewShas transporthandle shas) $
 					fetch
 				handlestdout fromh
diff --git a/RemoteDaemon/Transport/Ssh/Types.hs b/RemoteDaemon/Transport/Ssh/Types.hs
index fa6a55d3d..606e1a563 100644
--- a/RemoteDaemon/Transport/Ssh/Types.hs
+++ b/RemoteDaemon/Transport/Ssh/Types.hs
@@ -16,11 +16,11 @@ module RemoteDaemon.Transport.Ssh.Types (
 ) where
 
 import qualified Utility.SimpleProtocol as Proto
-import RemoteDaemon.Types (RefList)
+import Annex.ChangedRefs (ChangedRefs)
 
 data Notification
 	= READY
-	| CHANGED RefList
+	| CHANGED ChangedRefs
 
 instance Proto.Sendable Notification where
 	formatMessage READY = ["READY"]
diff --git a/RemoteDaemon/Types.hs b/RemoteDaemon/Types.hs
index ba88aa685..c0d74e038 100644
--- a/RemoteDaemon/Types.hs
+++ b/RemoteDaemon/Types.hs
@@ -5,7 +5,6 @@
  - Licensed under the GNU GPL version 3 or higher.
  -}
 
-{-# LANGUAGE TypeSynonymInstances, FlexibleInstances #-}
 {-# OPTIONS_GHC -fno-warn-orphans #-}
 
 module RemoteDaemon.Types where
@@ -15,6 +14,7 @@ import qualified Annex
 import qualified Git.Types as Git
 import qualified Utility.SimpleProtocol as Proto
 import Types.GitConfig
+import Annex.ChangedRefs (ChangedRefs)
 
 import Network.URI
 import Control.Concurrent
@@ -52,13 +52,11 @@ data Consumed
 	= PAUSE
 	| LOSTNET
 	| RESUME
-	| CHANGED RefList
+	| CHANGED ChangedRefs
 	| RELOAD
 	| STOP
 	deriving (Show)
 
-type RefList = [Git.Ref]
-
 instance Proto.Sendable Emitted where
 	formatMessage (CONNECTED remote) =
 		["CONNECTED", Proto.serialize remote]
@@ -100,10 +98,6 @@ instance Proto.Serializable RemoteURI where
 	serialize (RemoteURI u) = show u
 	deserialize = RemoteURI <$$> parseURI
 
-instance Proto.Serializable RefList where
-	serialize = unwords . map Git.fromRef
-	deserialize = Just . map Git.Ref . words
-
 instance Proto.Serializable Bool where
 	serialize False = "0"
 	serialize True = "1"