Generate shorter keys for WORM and URL, avoiding keys that are longer than used for SHA256, so as to not break on systems like Windows that have very small maximum path length limits.

Backend/WORM.hs

@@ -34,9 +34,8 @@ keyValue :: KeySource -> Annex (Maybe Key)
 keyValue source = do
 	stat <- liftIO $ getFileStatus $ contentLocation source
 	relf <- getTopFilePath <$> inRepo (toTopFilePath $ keyFilename source)
-	n <- genKeyName relf
 	return $ Just $ stubKey
-		{ keyName = n
+		{ keyName = genKeyName relf
 		, keyBackendName = name backend
 		, keySize = Just $ fromIntegral $ fileSize stat
 		, keyMtime = Just $ modificationTime stat