Add merge command - ease the process to push manifests to remote re…

…gistries from a set of images

Signed-off-by: Vincent Boulineau <vincent.boulineau@datadoghq.com>

cmd/crane/cmd/merge.go

@@ -0,0 +1,37 @@
+// 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 cmd
+
+import (
+	"log"
+
+	"github.com/google/go-containerregistry/pkg/crane"
+	"github.com/spf13/cobra"
+)
+
+// NewCmdMerge creates a new cobra.Command for the copy subcommand.
+func NewCmdMerge(options *[]crane.Option) *cobra.Command {
+	return &cobra.Command{
+		Use:     "merge SRC [SRC...] DST",
+		Aliases: []string{"mg"},
+		Short:   "Efficiently merge in an index manifest and copy images from sources to dst",
+		Args:    cobra.MinimumNArgs(2),
+		Run: func(_ *cobra.Command, args []string) {
+			if err := crane.Merge(args[:len(args)-1], args[len(args)-1], *options...); err != nil {
+				log.Fatal(err)
+			}
+		},
+	}
+}

cmd/crane/cmd/root.go

@@ -87,6 +87,7 @@ func New(use, short string, options []crane.Option) *cobra.Command {
 		NewCmdList(&options),
 		NewCmdManifest(&options),
 		NewCmdOptimize(&options),
+		NewCmdMerge(&options),
 		NewCmdPull(&options),
 		NewCmdPush(&options),
 		NewCmdRebase(&options),

pkg/crane/merge.go

@@ -0,0 +1,128 @@
+// 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 crane
+
+import (
+	"fmt"
+
+	"github.com/google/go-containerregistry/pkg/logs"
+	"github.com/google/go-containerregistry/pkg/name"
+	v1 "github.com/google/go-containerregistry/pkg/v1"
+	"github.com/google/go-containerregistry/pkg/v1/empty"
+	"github.com/google/go-containerregistry/pkg/v1/mutate"
+	"github.com/google/go-containerregistry/pkg/v1/remote"
+	"github.com/google/go-containerregistry/pkg/v1/types"
+)
+
+// Merge copies a remote image or index from src to dst by merging several images/indexes into a single one.
+func Merge(sources []string, dst string, opt ...Option) error {
+	o := makeOptions(opt...)
+
+	if len(sources) == 1 {
+		return Copy(sources[0], dst, opt...)
+	}
+
+	dstRef, err := name.ParseReference(dst, o.name...)
+	if err != nil {
+		return fmt.Errorf("parsing reference for %q: %v", dst, err)
+	}
+
+	logs.Progress.Printf("Building index from %v", sources)
+	// Build an image for each child from the base and append it to a new index to produce the result.
+	adds := make([]mutate.IndexAddendum, 0)
+	for _, src := range sources {
+		srcRef, err := name.ParseReference(src, o.name...)
+		if err != nil {
+			return fmt.Errorf("parsing reference %q: %v", src, err)
+		}
+
+		desc, err := remote.Get(srcRef, o.remote...)
+		if err != nil {
+			return fmt.Errorf("fetching %q: %v", src, err)
+		}
+
+		srcAdds, err := buildIndexAddendums(desc)
+		if err != nil {
+			return fmt.Errorf("unable to build index entry for src: %q: %v", src, err)
+		}
+		adds = append(adds, srcAdds...)
+	}
+
+	destIdx := mutate.IndexMediaType(mutate.AppendManifests(empty.Index, adds...), types.DockerManifestList)
+
+	logs.Progress.Printf("Copying from generated index to %v", dstRef)
+	return remote.WriteIndex(dstRef, destIdx, o.remote...)
+}
+
+func buildIndexAddendums(desc *remote.Descriptor) ([]mutate.IndexAddendum, error) {
+	adds := make([]mutate.IndexAddendum, 0)
+
+	switch desc.MediaType {
+	case types.OCIImageIndex, types.DockerManifestList:
+		idx, err := desc.ImageIndex()
+		if err != nil {
+			return nil, err
+		}
+
+		im, err := idx.IndexManifest()
+		if err != nil {
+			return nil, err
+		}
+
+		for _, imDesc := range im.Manifests {
+			img, err := idx.Image(imDesc.Digest)
+			if err != nil {
+				return nil, err
+			}
+
+			adds = append(adds, mutate.IndexAddendum{
+				Add: img,
+				Descriptor: v1.Descriptor{
+					URLs:        imDesc.URLs,
+					MediaType:   imDesc.MediaType,
+					Annotations: imDesc.Annotations,
+					Platform:    imDesc.Platform,
+				},
+			})
+		}
+	case types.DockerManifestSchema1, types.DockerManifestSchema1Signed:
+		return nil, fmt.Errorf("merging v1 manifest is not supported")
+	default:
+		img, err := desc.Image()
+		if err != nil {
+			return nil, err
+		}
+		cfg, err := img.ConfigFile()
+		if err != nil {
+			return nil, err
+		}
+
+		adds = append(adds, mutate.IndexAddendum{
+			Add: img,
+			Descriptor: v1.Descriptor{
+				URLs:        desc.URLs,
+				MediaType:   desc.MediaType,
+				Annotations: desc.Annotations,
+				Platform: &v1.Platform{
+					Architecture: cfg.Architecture,
+					OS:           cfg.OS,
+					OSVersion:    cfg.OSVersion,
+				},
+			},
+		})
+	}
+
+	return adds, nil
+}