free space checking

Free space checking is now done, for transfers of data for keys that have free space metadata.
(Notably, not for SHA* keys generated with git-annex 0.24 or earlier.)

The code is believed to work on Linux, FreeBSD, and OSX; check compile-time
messages to see if it is not enabled for your OS.

Command/Migrate.hs

@@ -55,7 +55,7 @@ perform file oldkey newbackend = do
 	case stored of
 		Nothing -> return Nothing
 		Just (newkey, _) -> do
-			ok <- getViaTmp newkey $ \t -> do
+			ok <- getViaTmpUnchecked newkey $ \t -> do
 				-- Make a hard link to the old backend's
 				-- cached key, to avoid wasting disk space.
 				liftIO $ createLink src t

Command/SetKey.hs

@@ -32,7 +32,8 @@ perform :: FilePath -> CommandPerform
 perform file = do
 	key <- cmdlineKey
 	-- the file might be on a different filesystem, so mv is used
-	-- rather than simply calling moveToObjectDir
+	-- rather than simply calling moveToObjectDir; disk space is also
+	-- checked this way.
 	ok <- getViaTmp key $ \dest -> do
 		if dest /= file
 			then liftIO $

Command/Unlock.hs

@@ -41,6 +41,8 @@ perform dest key = do
 	inbackend <- Backend.hasKey key
 	when (not inbackend) $
 		error "content not present"
+	
+	checkDiskSpace key
 
 	g <- Annex.gitRepo
 	let src = gitAnnexLocation g key