Use lower case hash directories for storing files on crippled filesystems, same as is already done for bare repositories.

* since this is a crippled filesystem anyway, git-annex doesn't use
  symlinks on it
* so there's no reason to use the mixed case hash directories that we're
  stuck using to avoid breaking everyone's symlinks to the content
* so we can do what is already done for all bare repos, and make non-bare
  repos on crippled filesystems use the all-lower case hash directories
* which are, happily, all 3 letters long, so they cannot conflict with
  mixed case hash directories
* so I was able to 100% fix this and even resuming `git annex add` in the
  test case will recover and it will all just work.

Command/Add.hs

@@ -168,13 +168,13 @@ undo file key e = do
 	-- fromAnnex could fail if the file ownership is weird
 	tryharder :: IOException -> Annex ()
 	tryharder _ = do
-		src <- inRepo $ gitAnnexLocation key
+		src <- calcRepo $ gitAnnexLocation key
 		liftIO $ moveFile src file
 
 {- Creates the symlink to the annexed content, returns the link target. -}
 link :: FilePath -> Key -> Bool -> Annex String
 link file key hascontent = handle (undo file key) $ do
-	l <- calcGitLink file key
+	l <- inRepo $ gitAnnexLink file key
 	replaceFile file $ makeAnnexLink l
 
 #ifndef __ANDROID__
@@ -206,7 +206,9 @@ cleanup file key hascontent = do
 	when hascontent $
 		logStatus key InfoPresent
 	ifM (isDirect <&&> pure hascontent)
-		( stageSymlink file =<< hashSymlink =<< calcGitLink file key
+		( do
+			l <- inRepo $ gitAnnexLink file key
+			stageSymlink file =<< hashSymlink l
 		, ifM (coreSymlinks <$> Annex.getGitConfig)
 			( do
 				_ <- link file key hascontent