display scanning message whenever reconcileStaged has enough files to chew on

Clear visible progress bar first.

Removed showSideActionAfter because it can't be used in reconcileStaged
(import loop). Instead, it counts the number of files it
processes and displays it after it's seen a sufficient to know it's
taking a while.

Sponsored-by: Dartmouth College's Datalad project

Annex/Concurrent.hs

@@ -100,23 +100,3 @@ mergeState st = do
 		uncurry addCleanupAction
 	Annex.Queue.mergeFrom st'
 	changeState $ \s -> s { errcounter = errcounter s + errcounter st' }
-
-{- Display a message, only when the action runs for a long enough
- - amount of time.
- - 
- - The action should not display any other messages, progress, etc;
- - if it did there could be some scrambling of the display since the
- - message display could happen at the same time as other output,
- - or after it.
- -}
-showSideActionAfter :: Microseconds -> String -> Annex a -> Annex a
-showSideActionAfter t m a = do
-	waiter <- liftIO $ async $ unboundDelay t
-	let display = liftIO (waitCatch waiter) >>= \case
-		Left _ -> return ()
-		Right _ -> showSideAction m
-	displayer <- liftIO . async =<< forkState display
-	let cleanup = do
-		liftIO $ cancel waiter
-		join (liftIO (wait displayer))
-	a `finally` cleanup