on second thought, unlock should fail if content is not present

Command/Unlock.hs

@@ -7,6 +7,7 @@
 
 module Command.Unlock where
 
+import Control.Monad (when)
 import Control.Monad.State (liftIO)
 import System.Directory hiding (copyFile)
 
@@ -32,15 +33,15 @@ seek = [withFilesInGit start]
  - content. -}
 start :: CommandStartString
 start file = isAnnexed file $ \(key, _) -> do
-	inbackend <- Backend.hasKey key
-	if not inbackend
-		then return Nothing
-		else do
 	showStart "unlock" file
 	return $ Just $ perform file key
 
 perform :: FilePath -> Key -> CommandPerform
 perform dest key = do
+	inbackend <- Backend.hasKey key
+	when (not inbackend) $
+		error "content not present"
+
 	g <- Annex.gitRepo
 	let src = annexLocation g key
 	liftIO $ removeFile dest

test.hs

@@ -218,7 +218,7 @@ test_lock = "git-annex unlock/lock" ~: intmpclonerepo $ do
 	-- regression test: unlock of not present file should skip it
 	annexed_notpresent annexedfile
 	r <- git_annex "unlock" ["-q", annexedfile]
-	r @? "unlock failed with not present file"
+	not r @? "unlock failed to fail with not present file"
 	annexed_notpresent annexedfile
 
 	git_annex "get" ["-q", annexedfile] @? "get of file failed"