fixed id parent on root on root

internal/types/id.go

@@ -69,9 +69,15 @@ func (i ID) Parent() *ID {
 			Key:    strings.Join(parts[:len(parts)-2], "/") + "/",
 		}
 	} else {
+		dir := filepath.Dir(i.Key)
+
+		if dir != "/" {
+			dir += "/"
+		}
+
 		parent = &ID{
 			Bucket: i.Bucket,
-			Key:    filepath.Dir(i.Key) + "/",
+			Key:    dir,
 		}
 	}