saving new turn

pkg/repo/repo.go

@@ -2,12 +2,26 @@ package repo
 
 import (
 	"encoding"
+	"errors"
 
 	"github.com/iliadenisov/galaxy/pkg/repo/fs"
 )
 
+type StorageError error
+
+func NewStorageError(err error) error {
+	return StorageError(err)
+}
+
+type StateError error
+
+func NewStateError(msg string) error {
+	return StateError(errors.New(msg))
+}
+
 type Storage interface {
 	Lock() (func() error, error)
+	Exist(string) (bool, error)
 	Write(string, encoding.BinaryMarshaler) error
 	Read(string, encoding.BinaryUnmarshaler) error
 }