immediate queue flushing when annex.queuesize=1

Previously, it only flushed when the queue got larger than 1.

Also, make the queue auto-flush when items are added, rather than needing
to be flushed as a separate step. This simplifies the code and make it more
efficient too, as it avoids needing to read the queue out of the state to
check if it should be flushed.

Assistant/Threads/Watcher.hs

@@ -195,11 +195,7 @@ runHandler handler file filestatus = void $ do
 	case r of
 		Left e -> liftIO $ warningIO $ show e
 		Right Nothing -> noop
-		Right (Just change) -> do
-			-- Just in case the commit thread is not
-			-- flushing the queue fast enough.
-			liftAnnex Annex.Queue.flushWhenFull
-			recordChange change
+		Right (Just change) -> recordChange change
   where
 	normalize f
 		| "./" `isPrefixOf` file = drop 2 f
@@ -391,7 +387,6 @@ onDelDir dir _ = do
 	recordChanges $ map (\f -> Change now f RmChange) fs
 
 	void $ liftIO clean
-	liftAnnex Annex.Queue.flushWhenFull
 	noChange
 
 {- Called when there's an error with inotify or kqueue. -}