make fsck normalize object locations

The purpose of this is to fix situations where the annex object file is
stored in a directory structure other than where annex symlinks point to.

But it will also move object files from the hashdirmixed back to
hashdirlower if the repo configuration makes that the normal location.
It would have been more work to avoid that than to let it do it.

Sponsored-by: Dartmouth College's Datalad project

Annex/Content.hs

@@ -64,6 +64,7 @@ module Annex.Content (
 	isKeyUnlockedThin,
 	getKeyStatus,
 	getKeyFileStatus,
+	cleanObjectDirs,
 ) where
 
 import System.IO.Unsafe (unsafeInterleaveIO)
@@ -610,6 +611,11 @@ cleanObjectLoc key cleaner = do
 	cleaner
 	cleanObjectDirs file
 
+{- Given a filename inside the object directory, tries to remove the object
+ - directory, as well as the object hash directories.
+ - 
+ - Does nothing if the object directory is not empty, and does not
+ - throw an exception if it's unable to remove a directory. -}
 cleanObjectDirs :: RawFilePath -> Annex ()
 cleanObjectDirs f = do
 	HashLevels n <- objectHashLevels <$> Annex.getGitConfig
@@ -619,7 +625,8 @@ cleanObjectDirs f = do
 	go file n = do
 		let dir = parentDir file
 		maybe noop (const $ go dir (n-1))
-			<=< catchMaybeIO $ removeDirectory (fromRawFilePath dir)
+			<=< catchMaybeIO $ tryWhenExists $
+				removeDirectory (fromRawFilePath dir)
 
 {- Removes a key's file from .git/annex/objects/ -}
 removeAnnex :: ContentRemovalLock -> Annex ()