assistant: Fix a race condition that could cause a pointer file to get ingested into the annex

This was caused by commit fb8ab2469d putting
an isPointerFile check in the wrong place. So if the file was not a pointer
file at that point, but got replaced by one before the file got locked
down, the pointer file would be ingested into the annex.

The fix is simply to move the isPointerFile check to after safeToAdd locks
down the file. Now if the file changes to a pointer file after the
isPointerFile check, ingestion will see that it changed after lockdown,
and will refuse to add it to the annex.

Sponsored-by: the NIH-funded NICEMAN (ReproNim TR&D3) project

Assistant/Threads/Committer.hs

@@ -290,19 +290,34 @@ handleAdds lockdowndir havelsof largefilematcher annexdotfiles delayadd cs = ret
 		refillChanges postponed
 
 	returnWhen (null toadd) $ do
+		(addedpointerfiles, toaddrest) <- partitionEithers
+			<$> mapM checkpointerfile toadd
 		(toaddannexed, toaddsmall) <- partitionEithers
-			<$> mapM checksmall toadd
+			<$> mapM checksmall toaddrest
 		addsmall toaddsmall
 		addedannexed <- addaction toadd $
 			catMaybes <$> addannexed toaddannexed
-		return $ addedannexed ++ toaddsmall ++ otherchanges
+		return $ addedannexed ++ toaddsmall ++ addedpointerfiles ++ otherchanges
   where
 	(incomplete, otherchanges) = partition (\c -> isPendingAddChange c || isInProcessAddChange c) cs
 
 	returnWhen c a
 		| c = return otherchanges
 		| otherwise = a
-
+	
+	checkpointerfile change = do
+		let file = toRawFilePath $ changeFile change
+		mk <- liftIO $ isPointerFile file
+		case mk of
+			Nothing -> return (Right change)
+			Just key -> do
+				mode <- liftIO $ catchMaybeIO $ fileMode <$> R.getFileStatus file
+				liftAnnex $ stagePointerFile file mode =<< hashPointerFile key
+				return $ Left $ Change
+					(changeTime change)
+					(changeFile change)
+					(LinkChange (Just key))
+	
 	checksmall change
 		| not annexdotfiles && dotfile f =
 			return (Right change)

Assistant/Threads/Watcher.hs

@@ -196,11 +196,8 @@ shouldRestage :: DaemonStatus -> Bool
 shouldRestage ds = scanComplete ds || forceRestage ds
 
 onAddFile :: Bool -> Handler
-onAddFile symlinkssupported f fs = do
-	mk <- liftIO $ isPointerFile $ toRawFilePath f
-	case mk of
-		Nothing -> onAddFile' contentchanged addassociatedfile addlink samefilestatus symlinkssupported f fs
-		Just k -> addlink f k
+onAddFile symlinkssupported f fs =
+	onAddFile' contentchanged addassociatedfile addlink samefilestatus symlinkssupported f fs
   where
 	addassociatedfile key file = 
 		Database.Keys.addAssociatedFile key