imagetools: metadata-file flag

Signed-off-by: CrazyMax <1951866+crazy-max@users.noreply.github.com>

commands/imagetools/create.go

@@ -5,6 +5,7 @@ import (
 	"encoding/json"
 	"fmt"
 	"os"
+	"sort"
 	"strings"
 
 	"github.com/containerd/containerd/v2/core/remotes"
@@ -16,7 +17,9 @@ import (
 	"github.com/docker/buildx/util/imagetools"
 	"github.com/docker/buildx/util/progress"
 	"github.com/docker/cli/cli/command"
+	"github.com/moby/buildkit/exporter/containerimage/exptypes"
 	"github.com/moby/buildkit/util/progress/progressui"
+	"github.com/moby/sys/atomicwriter"
 	"github.com/opencontainers/go-digest"
 	ocispecs "github.com/opencontainers/image-spec/specs-go/v1"
 	"github.com/pkg/errors"
@@ -34,6 +37,7 @@ type createOptions struct {
 	progress     string
 	preferIndex  bool
 	platforms    []string
+	metadataFile string
 }
 
 func runCreate(ctx context.Context, dockerCli command.Cli, in createOptions, args []string) error {
@@ -76,11 +80,16 @@ func runCreate(ctx context.Context, dockerCli command.Cli, in createOptions, arg
 	}
 
 	repos := map[string]struct{}{}
-
 	for _, t := range tags {
 		repos[t.Name()] = struct{}{}
 	}
 
+	repoNames := make([]string, 0, len(repos))
+	for repo := range repos {
+		repoNames = append(repoNames, repo)
+	}
+	sort.Strings(repoNames)
+
 	sourceRefs := false
 	for _, s := range srcs {
 		if s.Ref != nil {
@@ -241,6 +250,15 @@ func runCreate(ctx context.Context, dockerCli command.Cli, in createOptions, arg
 		err = err1
 	}
 
+	if err == nil && len(in.metadataFile) > 0 {
+		if err := writeMetadataFile(in.metadataFile, map[string]any{
+			exptypes.ExporterImageDescriptorKey: desc,
+			exptypes.ExporterImageNameKey:       strings.Join(repoNames, ","),
+		}); err != nil {
+			return err
+		}
+	}
+
 	return err
 }
 
@@ -348,6 +366,7 @@ func createCmd(dockerCli command.Cli, opts RootOptions) *cobra.Command {
 	flags.StringArrayVarP(&options.annotations, "annotation", "", []string{}, "Add annotation to the image")
 	flags.BoolVar(&options.preferIndex, "prefer-index", true, "When only a single source is specified, prefer outputting an image index or manifest list instead of performing a carbon copy")
 	flags.StringArrayVarP(&options.platforms, "platform", "p", []string{}, "Filter specified platforms of target image")
+	flags.StringVar(&options.metadataFile, "metadata-file", "", "Write create result metadata to a file")
 
 	return cmd
 }
@@ -367,3 +386,11 @@ func mergeDesc(d1, d2 ocispecs.Descriptor) (ocispecs.Descriptor, error) {
 	}
 	return d1, nil
 }
+
+func writeMetadataFile(filename string, dt any) error {
+	b, err := json.MarshalIndent(dt, "", "  ")
+	if err != nil {
+		return err
+	}
+	return atomicwriter.WriteFile(filename, b, 0o644)
+}

docs/reference/buildx_imagetools_create.md

@@ -9,18 +9,19 @@ Create a new image based on source images
 
 ### Options
 
-| Name                             | Type          | Default | Description                                                                                                                   |
+| Name                                | Type          | Default | Description                                                                                                                   |
-|:---------------------------------|:--------------|:--------|:------------------------------------------------------------------------------------------------------------------------------|
+|:------------------------------------|:--------------|:--------|:------------------------------------------------------------------------------------------------------------------------------|
-| [`--annotation`](#annotation)    | `stringArray` |         | Add annotation to the image                                                                                                   |
+| [`--annotation`](#annotation)       | `stringArray` |         | Add annotation to the image                                                                                                   |
-| [`--append`](#append)            | `bool`        |         | Append to existing manifest                                                                                                   |
+| [`--append`](#append)               | `bool`        |         | Append to existing manifest                                                                                                   |
-| [`--builder`](#builder)          | `string`      |         | Override the configured builder instance                                                                                      |
+| [`--builder`](#builder)             | `string`      |         | Override the configured builder instance                                                                                      |
-| `-D`, `--debug`                  | `bool`        |         | Enable debug logging                                                                                                          |
+| `-D`, `--debug`                     | `bool`        |         | Enable debug logging                                                                                                          |
-| [`--dry-run`](#dry-run)          | `bool`        |         | Show final image instead of pushing                                                                                           |
+| [`--dry-run`](#dry-run)             | `bool`        |         | Show final image instead of pushing                                                                                           |
-| [`-f`](#file), [`--file`](#file) | `stringArray` |         | Read source descriptor from file                                                                                              |
+| [`-f`](#file), [`--file`](#file)    | `stringArray` |         | Read source descriptor from file                                                                                              |
-| `-p`, `--platform`               | `stringArray` |         | Filter specified platforms of target image                                                                                    |
+| [`--metadata-file`](#metadata-file) | `string`      |         | Write create result metadata to a file                                                                                        |
-| `--prefer-index`                 | `bool`        | `true`  | When only a single source is specified, prefer outputting an image index or manifest list instead of performing a carbon copy |
+| `-p`, `--platform`                  | `stringArray` |         | Filter specified platforms of target image                                                                                    |
-| `--progress`                     | `string`      | `auto`  | Set type of progress output (`auto`, `none`, `plain`, `rawjson`, `tty`). Use plain to show container output                   |
+| `--prefer-index`                    | `bool`        | `true`  | When only a single source is specified, prefer outputting an image index or manifest list instead of performing a carbon copy |
-| [`-t`](#tag), [`--tag`](#tag)    | `stringArray` |         | Set reference for new image                                                                                                   |
+| `--progress`                        | `string`      | `auto`  | Set type of progress output (`auto`, `none`, `plain`, `rawjson`, `tty`). Use plain to show container output                   |
+| [`-t`](#tag), [`--tag`](#tag)       | `stringArray` |         | Set reference for new image                                                                                                   |
 
 
 <!---MARKER_GEN_END-->
@@ -100,6 +101,28 @@ The descriptor in the file is merged with existing descriptor in the registry if
 
 The supported fields for the descriptor are defined in [OCI spec](https://github.com/opencontainers/image-spec/blob/master/descriptor.md#properties) .
 
+### <a name="metadata-file"></a> Write create result metadata to a file (--metadata-file)
+
+To output metadata such as the image digest, pass the `--metadata-file` flag.
+The metadata will be written as a JSON object to the specified file. The
+directory of the specified file must already exist and be writable.
+
+```console
+$ docker buildx imagetools create -t user/app:latest -f image1 -f image2 --metadata-file metadata.json
+$ cat metadata.json
+```
+
+```json
+{
+  "containerimage.descriptor": {
+    "mediaType": "application/vnd.oci.image.index.v1+json",
+    "digest": "sha256:19ffeab6f8bc9293ac2c3fdf94ebe28396254c993aea0b5a542cfb02e0883fa3",
+    "size": 4654
+  },
+  "image.name": "docker.io/user/app"
+}
+```
+
 ### <a name="tag"></a> Set reference for new image  (-t, --tag)
 
 ```text

tests/imagetools.go

@@ -2,7 +2,10 @@ package tests
 
 import (
 	"encoding/json"
+	"os"
 	"os/exec"
+	"path"
+	"path/filepath"
 	"testing"
 
 	"github.com/containerd/containerd/v2/core/images"
@@ -50,10 +53,23 @@ func testImagetoolsCopyManifest(t *testing.T, sb integration.Sandbox) {
 	require.NoError(t, err)
 	target2 := registry2 + "/buildx/imtools2-manifest:latest"
 
-	cmd = buildxCmd(sb, withArgs("imagetools", "create", "-t", target2, target))
+	cmd = buildxCmd(sb, withArgs("imagetools", "create", "--metadata-file", path.Join(dir, "md.json"), "-t", target2, target))
 	dt, err = cmd.CombinedOutput()
 	require.NoError(t, err, string(dt))
 
+	mddt, err := os.ReadFile(filepath.Join(dir, "md.json"))
+	require.NoError(t, err)
+
+	type mdT struct {
+		ImageDescriptor ocispecs.Descriptor `json:"containerimage.descriptor"`
+		ImageName       string              `json:"image.name"`
+	}
+	var md mdT
+	err = json.Unmarshal(mddt, &md)
+	require.NoError(t, err)
+	require.NotEmpty(t, md.ImageDescriptor)
+	require.Equal(t, registry2+"/buildx/imtools2-manifest", md.ImageName)
+
 	cmd = buildxCmd(sb, withArgs("imagetools", "inspect", target2, "--raw"))
 	dt, err = cmd.CombinedOutput()
 	require.NoError(t, err, string(dt))
@@ -123,10 +139,23 @@ func testImagetoolsCopyIndex(t *testing.T, sb integration.Sandbox) {
 	require.NoError(t, err)
 	target2 := registry2 + "/buildx/imtools2:latest"
 
-	cmd = buildxCmd(sb, withArgs("imagetools", "create", "-t", target2, target))
+	cmd = buildxCmd(sb, withArgs("imagetools", "create", "--metadata-file", path.Join(dir, "md.json"), "-t", target2, target))
 	dt, err = cmd.CombinedOutput()
 	require.NoError(t, err, string(dt))
 
+	mddt, err := os.ReadFile(filepath.Join(dir, "md.json"))
+	require.NoError(t, err)
+
+	type mdT struct {
+		ImageDescriptor ocispecs.Descriptor `json:"containerimage.descriptor"`
+		ImageName       string              `json:"image.name"`
+	}
+	var md mdT
+	err = json.Unmarshal(mddt, &md)
+	require.NoError(t, err)
+	require.NotEmpty(t, md.ImageDescriptor)
+	require.Equal(t, registry2+"/buildx/imtools2", md.ImageName)
+
 	cmd = buildxCmd(sb, withArgs("imagetools", "inspect", target2, "--raw"))
 	dt, err = cmd.CombinedOutput()
 	require.NoError(t, err, string(dt))