image: Add `convert` command

Signed-off-by: Paweł Gronowski <pawel.gronowski@docker.com>

cli/command/image/cmd.go

@@ -27,6 +27,7 @@ func NewImageCommand(dockerCli command.Cli) *cobra.Command {
 		newRemoveCommand(dockerCli),
 		newInspectCommand(dockerCli),
 		NewPruneCommand(dockerCli),
+		NewConvertCommand(dockerCli),
 	)
 	return cmd
 }

cli/command/image/convert.go

@@ -0,0 +1,199 @@
+package image
+
+import (
+	"context"
+	"errors"
+	"fmt"
+
+	"github.com/containerd/platforms"
+	"github.com/distribution/reference"
+	"github.com/docker/cli/cli"
+	"github.com/docker/cli/cli/command"
+	"github.com/docker/docker/api/types/filters"
+	imagetypes "github.com/docker/docker/api/types/image"
+	"github.com/morikuni/aec"
+	"github.com/opencontainers/image-spec/specs-go"
+	v1 "github.com/opencontainers/image-spec/specs-go/v1"
+	"github.com/spf13/cobra"
+)
+
+type convertArgs struct {
+	Src            string
+	Dst            []string
+	Platforms      []string
+	NoAttestations bool
+	OnlyAvailable  bool
+}
+
+func NewConvertCommand(dockerCli command.Cli) *cobra.Command {
+	var args convertArgs
+
+	cmd := &cobra.Command{
+		Use:   "convert [OPTIONS]",
+		Short: "Convert multi-platform images",
+		Args:  cli.ExactArgs(0),
+		RunE: func(cmd *cobra.Command, _ []string) error {
+			return runConvert(cmd.Context(), dockerCli, args)
+		},
+		Aliases: []string{"convert"},
+		Annotations: map[string]string{
+			"aliases": "docker image convert, docker convert",
+		},
+	}
+
+	flags := cmd.Flags()
+	flags.StringArrayVar(&args.Platforms, "platforms", nil, "Include only the specified platforms in the destination image")
+	flags.BoolVar(&args.NoAttestations, "no-attestations", false, "Do not include image attestations")
+	flags.BoolVar(&args.OnlyAvailable, "available", false, "Only include manifests which blobs are available locally")
+	flags.StringArrayVar(&args.Dst, "to", nil, "Target image references")
+	flags.StringVar(&args.Src, "from", "", "Source image reference")
+
+	return cmd
+}
+
+type convertFilter = func(mfst imagetypes.ImageManifestSummary) bool
+
+func runConvert(ctx context.Context, dockerCLI command.Cli, args convertArgs) error {
+	if len(args.Dst) == 0 {
+		return errors.New("no destination image specified")
+	}
+	if args.Src == "" {
+		return errors.New("no source image specified")
+	}
+
+	matchesFilters, err := parseConvertFilters(args)
+	if err != nil {
+		return err
+	}
+
+	list, err := dockerCLI.Client().ImageList(ctx, imagetypes.ListOptions{
+		All:     true,
+		Filters: filters.NewArgs(filters.Arg("reference", args.Src)),
+	})
+	if err != nil {
+		return err
+	}
+
+	if len(list) == 0 {
+		return fmt.Errorf("no such image: %s", args.Src)
+	}
+
+	newManifests := make([]imagetypes.ImageManifestSummary, 0, len(list[0].Manifests))
+	for _, mfst := range list[0].Manifests {
+		if !matchesFilters(mfst) {
+			continue
+		}
+		newManifests = append(newManifests, mfst)
+	}
+
+	dstRefs := make([]reference.NamedTagged, 0, len(args.Dst))
+	for _, dst := range args.Dst {
+		dstRef, err := reference.ParseNormalizedNamed(dst)
+		if err != nil {
+			return fmt.Errorf("invalid destination image reference: %s: %w", dst, err)
+		}
+
+		dstRef = reference.TagNameOnly(dstRef)
+		dstRefTagged := dstRef.(reference.NamedTagged)
+
+		dstRefs = append(dstRefs, dstRefTagged)
+	}
+
+	newIndex := createIndex(newManifests)
+
+	desc, err := dockerCLI.Client().ImageCreateFromOCIIndex(ctx, dstRefs[0], newIndex)
+	if err != nil {
+		return err
+	}
+
+	fmt.Println(aec.Bold.Apply("New image digest:"), desc.Digest.String())
+	for idx, dst := range dstRefs {
+		ref := reference.FamiliarString(dst)
+		if idx > 0 {
+			err := dockerCLI.Client().ImageTag(ctx, dstRefs[0].String(), dst.String())
+			if err != nil {
+				fmt.Print(aec.LightRedF.Apply(" ✗ "), ref+" - "+aec.LightRedF.Apply(" tag failed: "+err.Error()))
+				continue
+			}
+		}
+
+		fmt.Println(aec.LightGreenF.Apply(" ✓ "), ref)
+	}
+
+	return nil
+}
+
+func createIndex(manifests []imagetypes.ImageManifestSummary) v1.Index {
+	idx := v1.Index{
+		Versioned: specs.Versioned{
+			SchemaVersion: 2,
+		},
+		MediaType: v1.MediaTypeImageIndex,
+	}
+
+	for _, mfst := range manifests {
+		idx.Manifests = append(idx.Manifests, mfst.Descriptor)
+	}
+	return idx
+}
+
+func parseConvertFilters(args convertArgs) (convertFilter, error) {
+	var flts []convertFilter
+
+	// args.Platforms
+	if len(args.Platforms) > 0 {
+		f, err := filterPlatforms(args.Platforms)
+		if err != nil {
+			return nil, err
+		}
+		flts = append(flts, f)
+	}
+
+	// args.NoAttestations
+	if args.NoAttestations {
+		flts = append(flts, func(mfst imagetypes.ImageManifestSummary) bool {
+			return mfst.Kind != imagetypes.ImageManifestKindAttestation
+		})
+	}
+
+	// args.OnlyAvailablePlatforms
+	if args.OnlyAvailable {
+		flts = append(flts, func(mfst imagetypes.ImageManifestSummary) bool {
+			return mfst.Available
+		})
+	}
+
+	matchesFilters := func(mfst imagetypes.ImageManifestSummary) bool {
+		for _, f := range flts {
+			if !f(mfst) {
+				return false
+			}
+		}
+		return true
+	}
+	return matchesFilters, nil
+}
+
+func filterPlatforms(platformStrs []string) (convertFilter, error) {
+	p := make([]v1.Platform, 0, len(platformStrs))
+	for _, platform := range platformStrs {
+		pl, err := platforms.Parse(platform)
+		if err != nil {
+			return nil, err
+		}
+		p = append(p, pl)
+	}
+	pm := platforms.Any(p...)
+
+	return func(mfst imagetypes.ImageManifestSummary) bool {
+		if mfst.Descriptor.Platform != nil {
+			return pm.Match(*mfst.Descriptor.Platform)
+		}
+
+		if mfst.Kind != imagetypes.ImageManifestKindImage {
+			return false
+		}
+
+		return pm.Match(mfst.ImageData.Platform)
+	}, nil
+}

docs/reference/commandline/image.md

@@ -8,6 +8,7 @@ Manage images
 | Name                          | Description                                                              |
 |:------------------------------|:-------------------------------------------------------------------------|
 | [`build`](image_build.md)     | Build an image from a Dockerfile                                         |
+| [`convert`](image_convert.md) | Convert multi-platform images                                            |
 | [`history`](image_history.md) | Show the history of an image                                             |
 | [`import`](image_import.md)   | Import the contents from a tarball to create a filesystem image          |
 | [`inspect`](image_inspect.md) | Display detailed information on one or more images                       |

docs/reference/commandline/image_convert.md

@@ -0,0 +1,22 @@
+# docker image convert
+
+<!---MARKER_GEN_START-->
+Convert multi-platform images
+
+### Aliases
+
+`docker image convert`, `docker convert`
+
+### Options
+
+| Name                | Type          | Default | Description                                                   |
+|:--------------------|:--------------|:--------|:--------------------------------------------------------------|
+| `--available`       | `bool`        |         | Only include manifests which blobs are available locally      |
+| `--from`            | `string`      |         | Source image reference                                        |
+| `--no-attestations` | `bool`        |         | Do not include image attestations                             |
+| `--platforms`       | `stringArray` |         | Include only the specified platforms in the destination image |
+| `--to`              | `stringArray` |         | Target image references                                       |
+
+
+<!---MARKER_GEN_END-->
+