clean empty object directories after deleting content lock file

When dropping content, this was already done after deleting the content
file, but the lock file prevents deleting the directories. So, try the
deletion again.

This does mean there's a small added overhead of a failed rmdir().

Sponsored-by: Dartmouth College's Datalad project

Annex/Content.hs

@@ -236,8 +236,9 @@ lockContentUsing locker sharedlock key fallback a = do
 #endif
 
 	cleanuplockfile lockfile = modifyContent lockfile $
-		void $ liftIO $ tryIO $
+		void $ liftIO $ tryIO $ do
 			removeWhenExistsWith R.removeLink lockfile
+			cleanObjectDirs lockfile
 
 {- Runs an action, passing it the temp file to get,
  - and if the action succeeds, verifies the file matches
@@ -574,12 +575,15 @@ cleanObjectLoc key cleaner = do
 	file <- calcRepo (gitAnnexLocation key)
 	void $ tryIO $ thawContentDir file
 	cleaner
-	liftIO $ removeparents file (3 :: Int)
+	liftIO $ cleanObjectDirs file
+
+cleanObjectDirs :: RawFilePath -> IO ()
+cleanObjectDirs = go (3 :: Int)
   where
-	removeparents _ 0 = noop
+	go 0 _ = noop
-	removeparents file n = do
+	go n file = do
 		let dir = parentDir file
-		maybe noop (const $ removeparents dir (n-1))
+		maybe noop (const $ go (n-1) dir)
 			<=< catchMaybeIO $ removeDirectory (fromRawFilePath dir)
 
 {- Removes a key's file from .git/annex/objects/ -}