disentangle concurrency and message type

This makes -Jn work with --json and --quiet, where before
setting -Jn disabled those options.

Concurrent json output is currently a mess though since threads output
chunks over top of one-another.

Messages/Internal.hs

@@ -12,25 +12,26 @@ import Annex
 import Types.Messages
 import Messages.Concurrent
 
-withOutputType :: (OutputType -> Annex a) -> Annex a
-withOutputType a = outputType <$> Annex.getState Annex.output >>= a
+withMessageState :: (MessageState -> Annex a) -> Annex a
+withMessageState a = Annex.getState Annex.output >>= a
 
 outputMessage :: IO () -> String -> Annex ()
-outputMessage json s = withOutputType go
-  where
-	go NormalOutput = liftIO $
-		flushed $ putStr s
-	go QuietOutput = q
-	go o@(ConcurrentOutput {}) = concurrentMessage o False s q
-	go JSONOutput = liftIO $ flushed json
+outputMessage json msg = withMessageState $ \s -> case outputType s of
+	NormalOutput
+		| concurrentOutputEnabled s -> concurrentMessage s False msg q
+		| otherwise -> liftIO $ flushed $ putStr msg
+	QuietOutput -> q
+	JSONOutput -> liftIO $ flushed json
 
 outputError :: String -> Annex ()
-outputError s = withOutputType go
+outputError msg = withMessageState $ \s ->
+	if concurrentOutputEnabled s
+		then concurrentMessage s True msg go
+		else go
   where
-	go o@(ConcurrentOutput {}) = concurrentMessage o True s (go NormalOutput)
-	go _ = liftIO $ do
+	go = liftIO $ do
 		hFlush stdout
-		hPutStr stderr s
+		hPutStr stderr msg
 		hFlush stderr
 
 q :: Monad m => m ()