reuse cached layer

pkg/commands/cache.go

@@ -0,0 +1,37 @@
+/*
+Copyright 2020 Google LLC
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+package commands
+
+import v1 "github.com/google/go-containerregistry/pkg/v1"
+
+type Cached interface {
+	Layer() v1.Layer
+	ReadSuccess() bool
+}
+
+type caching struct {
+	layer       v1.Layer
+	readSuccess bool
+}
+
+func (c caching) Layer() v1.Layer {
+	return c.layer
+}
+
+func (c caching) ReadSuccess() bool {
+	return c.readSuccess
+}