convert checkAvailable to use availability rather than localpath

Every remote that sets localpath also implements an availability that
reutrns Unavailable when a local directory is not available.

This makes external remotes, and others that get support for
availability Unavailable to be used by checkAvailable. (Which is only
used by the assistant.)

Had to keep localpath though, since other parts of the assistant use it
to eg, sync with a remote when a removable drive is plugged in.

Sponsored-by: Jack Hill on Patreon

Assistant/Sync.hs

@@ -59,11 +59,11 @@ import Control.Concurrent.Async
 reconnectRemotes :: [Remote] -> Assistant ()
 reconnectRemotes [] = recordExportCommit
 reconnectRemotes rs = void $ do
-	rs' <- liftIO $ filterM (Remote.checkAvailable True) rs
+	rs' <- liftAnnex $ filterM (Remote.checkAvailable True) rs
 	unless (null rs') $ do
 		failedrs <- syncAction rs' (const go)
 		forM_ failedrs $ \r ->
-			whenM (liftIO $ Remote.checkAvailable False r) $
+			whenM (liftAnnex $ Remote.checkAvailable False r) $
 				repoHasProblem (Remote.uuid r) (syncRemote r)
 		mapM_ signal $ filter (`notElem` failedrs) rs'
 	recordExportCommit

Assistant/Threads/Exporter.hs

@@ -51,7 +51,7 @@ exportThread = namedThread "Exporter" $ runEvery (Seconds 30) <~> do
  - to avoid ugly messages when a removable drive is not attached.
  -}
 exportTargets :: Assistant [Remote]
-exportTargets = liftIO . filterM (Remote.checkAvailable True)
+exportTargets = liftAnnex . filterM (Remote.checkAvailable True)
 	=<< candidates <$> getDaemonStatus
   where
 	candidates = filter (not . Remote.readonly) . exportRemotes

Assistant/Threads/ProblemFixer.hs

@@ -56,7 +56,7 @@ handleRemoteProblem urlrenderer rmt = do
 handleRemoteProblem' :: Git.Repo -> UrlRenderer -> Remote -> Assistant Bool
 handleRemoteProblem' repo urlrenderer rmt
 	| Git.repoIsLocal repo && not (Git.repoIsLocalUnknown repo) =
-		ifM (liftIO $ checkAvailable True rmt)
+		ifM (liftAnnex $ checkAvailable True rmt)
 			( do
 				fixedlocks <- repairStaleGitLocks repo
 				fsckresults <- showFscking urlrenderer (Just rmt) $ tryNonAsync $

Assistant/Threads/Pusher.hs

@@ -44,7 +44,7 @@ pushThread = namedThread "Pusher" $ runEvery (Seconds 2) <~> do
  - to avoid ugly messages when a removable drive is not attached.
  -}
 pushTargets :: Assistant [Remote]
-pushTargets = liftIO . filterM (Remote.checkAvailable True)
+pushTargets = liftAnnex . filterM (Remote.checkAvailable True)
 	=<< candidates <$> getDaemonStatus
   where
 	candidates = filter (not . Remote.readonly) . syncGitRemotes

Remote.hs

@@ -411,9 +411,12 @@ byCost = map snd . sortBy (comparing fst) . M.toList . costmap
 	costmap = M.fromListWith (++) . map costpair
 	costpair r = (cost r, [r])
 
-checkAvailable :: Bool -> Remote -> IO Bool
-checkAvailable assumenetworkavailable = 
-	maybe (return assumenetworkavailable) doesDirectoryExist . localpath
+checkAvailable :: Bool -> Remote -> Annex Bool
+checkAvailable assumenetworkavailable r = tryNonAsync (availability r) >>= \case
+	Left _e -> return assumenetworkavailable
+	Right LocallyAvailable -> return True
+	Right GloballyAvailable -> return assumenetworkavailable
+	Right Unavailable -> return False
 
 hasKey :: Remote -> Key -> Annex (Either String Bool)
 hasKey r k = either (Left  . show) Right <$> tryNonAsync (checkPresent r k)