suggest when user may want annex.stalldetection

When annex.stalldetection is not enabled, and a likely stall is detected,
display a suggestion to enable it.

Note that the progress meter display is not taken down when displaying
the message, so it will display like this:

	0%    8 B                 0 B/s
	  Transfer seems to have stalled. To handle stalling transfers, configure annex.stalldetection
	0%    10 B                0 B/s

Although of course if it's really stalled, it will never update
again after the message. Taking down the progress meter and starting
a new one doesn't seem too necessary given how unusual this is,
also this does help show the state it was at when it stalled.

Use of uninterruptibleCancel here is ok, the thread it's canceling
only does STM transactions and sleeps. The annex thread that gets
forked off is separate to avoid it being canceled, so that it
can be joined back at the end.

A module cycle required moving from dupState the precaching of the
remote list. Doing it at startConcurrency should cover all the cases
where the remote list is used in concurrent actions.

This commit was sponsored by Kevin Mueller on Patreon.

Annex/StallDetection.hs

@@ -15,9 +15,13 @@ import Utility.DataUnits
 import Utility.ThreadScheduler
 
 import Control.Concurrent.STM
+import Control.Monad.IO.Class (MonadIO)
 
-detectStalls :: Maybe StallDetection -> TVar (Maybe BytesProcessed) -> IO () -> IO ()
+{- This may be safely canceled (with eg uninterruptibleCancel),
+ - as long as the passed action can be safely canceled. -}
+detectStalls :: (Monad m, MonadIO m) => Maybe StallDetection -> TVar (Maybe BytesProcessed) -> m () -> m ()
 detectStalls Nothing _ _ = noop
+detectStalls (Just StallDetectionDisabled) _ _ = noop
 detectStalls (Just (StallDetection minsz duration)) metervar onstall =
 	detectStalls' minsz duration metervar onstall Nothing
 detectStalls (Just ProbeStallDetection) metervar onstall = do
@@ -30,7 +34,7 @@ detectStalls (Just ProbeStallDetection) metervar onstall = do
 	ontimelyadvance v $ \v' -> ontimelyadvance v' $
 		detectStalls' 1 duration metervar onstall
   where
-	getval = atomically $ fmap fromBytesProcessed
+	getval = liftIO $ atomically $ fmap fromBytesProcessed
 		<$> readTVar metervar
 	
 	duration = Duration 60
@@ -38,29 +42,30 @@ detectStalls (Just ProbeStallDetection) metervar onstall = do
 	delay = Seconds (fromIntegral (durationSeconds duration) `div` 2)
 	
 	waitforfirstupdate startval = do
-		threadDelaySeconds delay
+		liftIO $ threadDelaySeconds delay
 		v <- getval
 		if v > startval
 			then return v
 			else waitforfirstupdate startval
 
 	ontimelyadvance v cont = do
-		threadDelaySeconds delay
+		liftIO $ threadDelaySeconds delay
 		v' <- getval
 		when (v' > v) $
 			cont v'
 
 detectStalls'
-	:: ByteSize
+	:: (Monad m, MonadIO m)
+	=> ByteSize
 	-> Duration
 	-> TVar (Maybe BytesProcessed)
-	-> IO ()
+	-> m ()
 	-> Maybe ByteSize
-	-> IO ()
+	-> m ()
 detectStalls' minsz duration metervar onstall st = do
-	threadDelaySeconds delay
+	liftIO $ threadDelaySeconds delay
 	-- Get whatever progress value was reported most recently, if any.
-	v <- atomically $ fmap fromBytesProcessed
+	v <- liftIO $ atomically $ fmap fromBytesProcessed
 		<$> readTVar metervar
 	let cont = detectStalls' minsz duration metervar onstall v
 	case (st, v) of