Update vendor

vendor/github.com/google/go-containerregistry/pkg/v1/empty/image.go

@@ -0,0 +1,52 @@
+// Copyright 2018 Google LLC All Rights Reserved.
+//
+// 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 empty
+
+import (
+	"fmt"
+
+	v1 "github.com/google/go-containerregistry/pkg/v1"
+	"github.com/google/go-containerregistry/pkg/v1/partial"
+	"github.com/google/go-containerregistry/pkg/v1/types"
+)
+
+// Image is a singleton empty image, think: FROM scratch.
+var Image, _ = partial.UncompressedToImage(emptyImage{})
+
+type emptyImage struct{}
+
+// MediaType implements partial.UncompressedImageCore.
+func (i emptyImage) MediaType() (types.MediaType, error) {
+	return types.DockerManifestSchema2, nil
+}
+
+// RawConfigFile implements partial.UncompressedImageCore.
+func (i emptyImage) RawConfigFile() ([]byte, error) {
+	return partial.RawConfigFile(i)
+}
+
+// ConfigFile implements v1.Image.
+func (i emptyImage) ConfigFile() (*v1.ConfigFile, error) {
+	return &v1.ConfigFile{
+		RootFS: v1.RootFS{
+			// Some clients check this.
+			Type: "layers",
+		},
+	}, nil
+}
+
+func (i emptyImage) LayerByDiffID(h v1.Hash) (partial.UncompressedLayer, error) {
+	return nil, fmt.Errorf("LayerByDiffID(%s): empty image", h)
+}