some working code

Signed-off-by: Xiaoxuan Wang <xiaoxuanwang@microsoft.com>

cmd/oras/root/manifest/index/update.go

@@ -22,10 +22,12 @@ import (
 	"fmt"
 	"strings"
 
+	"github.com/opencontainers/go-digest"
 	ocispec "github.com/opencontainers/image-spec/specs-go/v1"
 	"github.com/spf13/cobra"
 	"oras.land/oras-go/v2"
 	"oras.land/oras-go/v2/errdef"
+	"oras.land/oras/cmd/oras/internal/argument"
 	"oras.land/oras/cmd/oras/internal/command"
 	oerrors "oras.land/oras/cmd/oras/internal/errors"
 	"oras.land/oras/cmd/oras/internal/option"
@@ -36,21 +38,26 @@ type updateOptions struct {
 	option.Common
 	option.Target
 
-	extraRefs    []string
-	addArguments []string
+	extraRefs       []string
+	addArguments    []string
+	mergeArguments  []string
+	removeArguments []string
 }
 
 func updateCmd() *cobra.Command {
 	var opts updateOptions
 	cmd := &cobra.Command{
-		Use:   "update <name>{:<tag>|@<digest>} {--add} {<tag>|<digest>} [...]",
-		Short: "Update an image index",
-		Long: `Update an image index and push to the repository or OCI image layout
+		Use:   "update <name>{:<tag>|@<digest>} {--add/--merge/--remove} {<tag>|<digest>} [...]",
+		Short: "[Experimental] Update and push an image index",
+		Long: `[Experimental] Update and push an image index
 		
-Example - add one manifest from an index:
-  oras manifest index update localhost:5000/hello:latest --add sha256:xxx
+Example - add one manifest and remove two manifests from an index tagged 'latest':
+  oras manifest index update localhost:5000/hello:latest --add sha256:xxx --remove sha256:xxx
+
+Example - remove a manifest and merge manifests from indexes tagged as 'index01' and 'index02':
+  oras manifest index update localhost:5000/hello:latest --remove sha256:xxx --merge index01 --merge index02
   `,
-		Args: cobra.MinimumNArgs(1),
+		Args: oerrors.CheckArgs(argument.AtLeast(1), "the destination index to update"),
 		PreRunE: func(cmd *cobra.Command, args []string) error {
 			refs := strings.Split(args[0], ",")
 			opts.RawReference = refs[0]
@@ -63,13 +70,15 @@ Example - add one manifest from an index:
 	}
 	option.ApplyFlags(&opts, cmd.Flags())
 	cmd.Flags().StringArrayVarP(&opts.addArguments, "add", "", nil, "add manifests to the index")
+	cmd.Flags().StringArrayVarP(&opts.mergeArguments, "merge", "", nil, "merge the manifests of another index")
+	cmd.Flags().StringArrayVarP(&opts.removeArguments, "remove", "", nil, "manifests to remove from the index")
 	return oerrors.Command(cmd, &opts.Target)
 }
 
 func updateIndex(cmd *cobra.Command, opts updateOptions) error {
 	// if --add is not used, then there's nothing to update
-	if !cmd.Flags().Changed("add") {
-		opts.Println("--add is not used. There's nothing to update.")
+	if !cmd.Flags().Changed("add") && !cmd.Flags().Changed("remove") && !cmd.Flags().Changed("merge") {
+		opts.Println("No update flag is used. There's nothing to update.")
 		return nil
 	}
 	ctx, logger := command.GetLogger(cmd, &opts.Common)
@@ -80,7 +89,7 @@ func updateIndex(cmd *cobra.Command, opts updateOptions) error {
 	if err := opts.EnsureReferenceNotEmpty(cmd, true); err != nil {
 		return err
 	}
-	// if a digest is given as the index reference, we need to ignore it
+	// if a digest is given as the index reference, we need to ignore it to successfully push
 	opts.RawReference, _, _ = strings.Cut(opts.RawReference, "@")
 	index, err := fetchIndex(ctx, target, opts)
 	if err != nil {
@@ -90,6 +99,14 @@ func updateIndex(cmd *cobra.Command, opts updateOptions) error {
 	if err != nil {
 		return err
 	}
+	manifests, err = mergeIndexes(ctx, manifests, target, opts)
+	if err != nil {
+		return err
+	}
+	manifests, err = removeManifests(ctx, manifests, target, opts.removeArguments)
+	if err != nil {
+		return err
+	}
 	desc, content, err := packIndex(&index, manifests)
 	if err != nil {
 		return err
@@ -134,3 +151,47 @@ func addManifests(ctx context.Context, manifests []ocispec.Descriptor, target or
 	}
 	return manifests, nil
 }
+
+func mergeIndexes(ctx context.Context, manifests []ocispec.Descriptor, target oras.ReadOnlyTarget, opts updateOptions) ([]ocispec.Descriptor, error) {
+	for _, index := range opts.mergeArguments {
+		desc, content, err := oras.FetchBytes(ctx, target, index, oras.DefaultFetchBytesOptions)
+		if err != nil {
+			if errors.Is(err, errdef.ErrNotFound) {
+				return nil, fmt.Errorf("could not resolve %s. Make sure the manifest exists in %s", index, opts.Path)
+			}
+			return nil, err
+		}
+		if desc.MediaType != ocispec.MediaTypeImageIndex {
+			return nil, fmt.Errorf("%s is not an image index", index)
+		}
+		opts.Println("Resolved index", index)
+		var index ocispec.Index
+		if err := json.Unmarshal(content, &index); err != nil {
+			return nil, err
+		}
+		manifests = append(manifests, index.Manifests...)
+	}
+	return manifests, nil
+}
+
+func removeManifests(ctx context.Context, manifests []ocispec.Descriptor, target oras.ReadOnlyTarget, removes []string) ([]ocispec.Descriptor, error) {
+	set := make(map[digest.Digest]struct{})
+	for _, rem := range removes {
+		desc, _, err := oras.FetchBytes(ctx, target, rem, oras.DefaultFetchBytesOptions)
+		if err != nil {
+			return nil, err
+		}
+		set[desc.Digest] = struct{}{}
+	}
+	pointer := len(manifests) - 1
+	for i, m := range manifests {
+		if _, exists := set[m.Digest]; exists {
+			// swap the to-be-removed manifest to the end of slice
+			manifests[i] = manifests[pointer]
+			pointer = pointer - 1
+		}
+	}
+	// shrink the slice to remove the manifests
+	manifests = manifests[:pointer+1]
+	return manifests, nil
+}