instead of os.rename, io.WriteFile and os.Remove

cmd/main.go

@@ -68,7 +68,20 @@ func merge(filepath string, mergeTargetFilePath string) error {
 	if err != nil {
 		return err
 	}
-	return os.Rename(tmppath, filepath)
+	return rename(tmppath, filepath)
+}
+
+func rename(oldpath, newpath string) error {
+	b, err := io.ReadFile(oldpath)
+	if err != nil {
+		return err
+	}
+
+	if err := io.WriteFile(b, newpath, os.ModePerm); err != nil {
+		return err
+	}
+
+	return os.Remove(oldpath)
 }
 
 func marshalRootToTempFile(root pttodo.Root) (string, error) {