send notifications when the TransferQueue is changed

The fun part was making it move things from TransferQueue to currentTransfers
entirely atomically. Which will avoid inconsistent display if the WebApp
renders the current status at just the wrong time. STM to the rescue!

Assistant/Threads/TransferScanner.hs

@@ -11,6 +11,7 @@ import Assistant.Common
 import Assistant.ScanRemotes
 import Assistant.TransferQueue
 import Assistant.ThreadedMonad
+import Assistant.DaemonStatus
 import Logs.Transfer
 import Logs.Location
 import qualified Remote
@@ -25,20 +26,20 @@ thisThread = "TransferScanner"
 {- This thread waits until a remote needs to be scanned, to find transfers
  - that need to be made, to keep data in sync.
  -}
-transferScannerThread :: ThreadState -> ScanRemoteMap -> TransferQueue -> IO ()
-transferScannerThread st scanremotes transferqueue = do
+transferScannerThread :: ThreadState -> DaemonStatusHandle -> ScanRemoteMap -> TransferQueue -> IO ()
+transferScannerThread st dstatus scanremotes transferqueue = do
 	runEvery (Seconds 2) $ do
 		r <- getScanRemote scanremotes
 		liftIO $ debug thisThread ["starting scan of", show r]
-		scan st transferqueue r
+		scan st dstatus transferqueue r
 		liftIO $ debug thisThread ["finished scan of", show r]
 	where
 
 {- This is a naive scan through the git work tree.
  - 
  - The scan is blocked when the transfer queue gets too large. -}
-scan :: ThreadState -> TransferQueue -> Remote -> IO ()
-scan st transferqueue r = do
+scan :: ThreadState -> DaemonStatusHandle -> TransferQueue -> Remote -> IO ()
+scan st dstatus transferqueue r = do
 	g <- runThreadState st $ fromRepo id
 	files <- LsFiles.inRepo [] g
 	go files
@@ -63,7 +64,7 @@ scan st transferqueue r = do
 					| otherwise = return Nothing
 				
 		u = Remote.uuid r
-		enqueue f t = queueTransferAt smallsize Later transferqueue (Just f) t r
+		enqueue f t = queueTransferAt smallsize Later transferqueue dstatus (Just f) t r
 		smallsize = 10
 
 		{- Look directly in remote for the key when it's cheap;