first pass at assistant knowing about export remotes

Split exportRemotes out from syncDataRemotes; the parts of the assistant
that upload keys and drop keys from remotes don't apply to exports,
because those operations are not supported.

Some parts of the assistant and webapp do operate on both
syncDataRemotes and exportRemotes. Particularly when downloading from
either of them. Added a downloadRemotes that combines both.

With this, the assistant should download from exports, but it won't yet
upload changes to them.

This commit was sponsored by Fernando Jimenez on Patreon.

Assistant/TransferQueue.hs

@@ -66,9 +66,7 @@ queueTransfersMatching matching reason schedule k f direction
 	| otherwise = go
   where
 	go = do
-		
-		rs <- liftAnnex . selectremotes
-			=<< syncDataRemotes <$> getDaemonStatus
+		rs <- liftAnnex . selectremotes =<< getDaemonStatus
 		let matchingrs = filter (matching . Remote.uuid) rs
 		if null matchingrs
 			then do
@@ -78,20 +76,21 @@ queueTransfersMatching matching reason schedule k f direction
 				forM_ matchingrs $ \r ->
 					enqueue reason schedule (gentransfer r) (stubInfo f r)
 				return True
-	selectremotes rs
+	selectremotes st
 		{- Queue downloads from all remotes that
 		 - have the key. The list of remotes is ordered with
 		 - cheapest first. More expensive ones will only be tried
 		 - if downloading from a cheap one fails. -}
 		| direction == Download = do
 			s <- locs
-			return $ filter (inset s) rs
+			return $ filter (inset s) (downloadRemotes st)
 		{- Upload to all remotes that want the content and don't
 		 - already have it. -}
 		| otherwise = do
 			s <- locs
 			filterM (wantSend True (Just k) f . Remote.uuid) $
-				filter (\r -> not (inset s r || Remote.readonly r)) rs
+				filter (\r -> not (inset s r || Remote.readonly r))
+					(syncDataRemotes st)
 	  where
 		locs = S.fromList <$> Remote.keyLocations k
 		inset s r = S.member (Remote.uuid r) s
@@ -114,7 +113,7 @@ queueDeferredDownloads :: Reason -> Schedule -> Assistant ()
 queueDeferredDownloads reason schedule = do
 	q <- getAssistant transferQueue
 	l <- liftIO $ atomically $ readTList (deferreddownloads q)
-	rs <- syncDataRemotes <$> getDaemonStatus
+	rs <- downloadRemotes <$> getDaemonStatus
 	left <- filterM (queue rs) l
 	unless (null left) $
 		liftIO $ atomically $ appendTList (deferreddownloads q) left