fix build warning

A recent change made plumbing the backend through fsck unncessary.

Left fsck checking backend and skipping operating on key when it could
not find one, although I'm not sure if that's necessary to support eg,
keys with unknown backend.

Command/Fsck.hs

@@ -128,7 +128,7 @@ start from inc si file key = Backend.getBackend (fromRawFilePath file) key >>= \
 		(numcopies, _mincopies) <- getFileNumMinCopies file
 		case from of
 			Nothing -> go $ perform key file backend numcopies
-			Just r -> go $ performRemote key afile backend numcopies r
+			Just r -> go $ performRemote key afile numcopies r
   where
 	go = runFsck inc si (mkActionItem (key, afile)) key
 	afile = AssociatedFile (Just file)
@@ -145,7 +145,7 @@ perform key file backend numcopies = do
 		, verifyAssociatedFiles key keystatus file
 		, verifyWorkTree key file
 		, checkKeySize key keystatus ai
-		, checkBackend backend key keystatus afile
+		, checkBackend key keystatus afile
 		, checkKeyUpgrade backend key ai afile
 		, checkKeyNumCopies key afile numcopies
 		]
@@ -155,8 +155,8 @@ perform key file backend numcopies = do
 
 {- To fsck a remote, the content is retrieved to a tmp file,
  - and checked locally. -}
-performRemote :: Key -> AssociatedFile -> Backend -> NumCopies -> Remote -> Annex Bool
-performRemote key afile backend numcopies remote =
+performRemote :: Key -> AssociatedFile -> NumCopies -> Remote -> Annex Bool
+performRemote key afile numcopies remote =
 	dispatch =<< Remote.hasKey remote key
   where
 	dispatch (Left err) = do
@@ -179,7 +179,7 @@ performRemote key afile backend numcopies remote =
 		, case fmap snd lv of
 			Just Verified -> return True
 			_ -> withLocalCopy (fmap fst lv) $
-				checkBackendRemote backend key remote ai
+				checkBackendRemote key remote ai
 		, checkKeyNumCopies key afile numcopies
 		]
 	ai = mkActionItem (key, afile)
@@ -218,16 +218,16 @@ startKey from inc (si, key, ai) numcopies =
 		Nothing -> stop
 		Just backend -> runFsck inc si ai key $
 			case from of
-				Nothing -> performKey key backend numcopies
-				Just r -> performRemote key (AssociatedFile Nothing) backend numcopies r
+				Nothing -> performKey key numcopies
+				Just r -> performRemote key (AssociatedFile Nothing) numcopies r
 
-performKey :: Key -> Backend -> NumCopies -> Annex Bool
-performKey key backend numcopies = do
+performKey :: Key -> NumCopies -> Annex Bool
+performKey key numcopies = do
 	keystatus <- getKeyStatus key
 	check
 		[ verifyLocationLog key keystatus (mkActionItem key)
 		, checkKeySize key keystatus (mkActionItem key)
-		, checkBackend backend key keystatus (AssociatedFile Nothing)
+		, checkBackend key keystatus (AssociatedFile Nothing)
 		, checkKeyNumCopies key (AssociatedFile Nothing) numcopies
 		]
 
@@ -501,14 +501,14 @@ checkKeyUpgrade _ _ _ (AssociatedFile Nothing) =
  - Thus when the user modifies the file, the object will be modified and
  - not pass the check, and we don't want to find an error in this case.
  -}
-checkBackend :: Backend -> Key -> KeyStatus -> AssociatedFile -> Annex Bool
-checkBackend backend key keystatus afile = do
+checkBackend :: Key -> KeyStatus -> AssociatedFile -> Annex Bool
+checkBackend key keystatus afile = do
 	content <- calcRepo (gitAnnexLocation key)
 	ifM (pure (isKeyUnlockedThin keystatus) <&&> (not <$> isUnmodified key content))
 		( nocheck
 		, do
 			mic <- withTSDelta (liftIO . genInodeCache content)
-			ifM (checkBackendOr badContent backend key content ai)
+			ifM (checkBackendOr badContent key content ai)
 				( do
 					checkInodeCache key content mic ai
 					return True
@@ -520,12 +520,12 @@ checkBackend backend key keystatus afile = do
 
 	ai = mkActionItem (key, afile)
 
-checkBackendRemote :: Backend -> Key -> Remote -> ActionItem -> RawFilePath -> Annex Bool
-checkBackendRemote backend key remote ai localcopy =
-	checkBackendOr (badContentRemote remote localcopy) backend key localcopy ai
+checkBackendRemote :: Key -> Remote -> ActionItem -> RawFilePath -> Annex Bool
+checkBackendRemote key remote ai localcopy =
+	checkBackendOr (badContentRemote remote localcopy) key localcopy ai
 
-checkBackendOr :: (Key -> Annex String) -> Backend -> Key -> RawFilePath -> ActionItem -> Annex Bool
-checkBackendOr bad backend key file ai = do
+checkBackendOr :: (Key -> Annex String) -> Key -> RawFilePath -> ActionItem -> Annex Bool
+checkBackendOr bad key file ai = do
 	ok <- verifyKeyContent' key file
 	unless ok $ do
 		msg <- bad key

Command/Migrate.hs

@@ -126,7 +126,7 @@ perform onlytweaksize o file oldkey oldkeyrec oldbackend newbackend = go =<< gen
 		| knowngoodcontent = finish =<< tweaksize newkey
 		| otherwise = stopUnless checkcontent $
 			finish =<< tweaksize newkey
-	checkcontent = Command.Fsck.checkBackend oldbackend oldkey KeyPresent afile
+	checkcontent = Command.Fsck.checkBackend oldkey KeyPresent afile
 	finish newkey = ifM (Command.ReKey.linkKey file oldkey newkey)
 		( do
 			_ <- copyMetaData oldkey newkey