Implement an experimental "copy image" function which calls an extension on Docker Hub to mount a manifest from one repo to another

ociclient/writer.go

@@ -46,7 +46,6 @@ func (c *Client) PushManifest(ctx context.Context, repo string, contents []byte,
 		Digest:    dig,
 		Size:      int64(len(contents)),
 		MediaType: mediaType,
-		Data:      contents,
 	}
 
 	var tags []string
@@ -57,14 +56,14 @@ func (c *Client) PushManifest(ctx context.Context, repo string, contents []byte,
 	// If there are no tags, push once by digest.
 	// If there are tags, push once per tag (all referencing the same contents).
 	if len(tags) == 0 {
-		_, err := c.putManifest(ctx, repo, desc.Digest.String(), nil, desc)
+		_, err := c.putManifest(ctx, repo, desc.Digest.String(), nil, desc, contents)
 		return desc, err
 	} else {
-		createdTags, err := c.putManifest(ctx, repo, desc.Digest.String(), tags, desc)
+		createdTags, err := c.putManifest(ctx, repo, desc.Digest.String(), tags, desc, contents)
 		if err != nil || len(createdTags) != len(tags) {
 			// bulk send failed, fallback to sending one at a time
 			for _, tag := range tags {
-				_, err = c.putManifest(ctx, repo, tag, nil, desc)
+				_, err = c.putManifest(ctx, repo, tag, nil, desc, contents)
 				if err != nil {
 					return oci.Descriptor{}, fmt.Errorf("creating tag %s failed: %w", tag, err)
 				}
@@ -74,16 +73,9 @@ func (c *Client) PushManifest(ctx context.Context, repo string, contents []byte,
 	return desc, nil
 }
 
-func (c *Client) putManifest(ctx context.Context, repo string, tagOrDigest string, tags []string, desc oci.Descriptor) ([]string, error) {
-	u := manifestURL(repo, tagOrDigest)
-	if len(tags) > 0 {
-		q := make(url.Values)
-		for _, tag := range tags {
-			q.Add("tag", tag)
-		}
-		u += "?" + q.Encode()
-	}
-	req, err := newRequest(ctx, http.MethodPut, u, bytes.NewReader(desc.Data), pushScope(repo))
+func (c *Client) putManifest(ctx context.Context, repo string, tagOrDigest string, tags []string, desc oci.Descriptor, contents []byte) ([]string, error) {
+	u := manifestURLWithTags(repo, tagOrDigest, tags)
+	req, err := newRequest(ctx, http.MethodPut, u, bytes.NewReader(contents), pushScope(repo))
 	if err != nil {
 		return nil, err
 	}
@@ -104,6 +96,43 @@ func (c *Client) putManifest(ctx context.Context, repo string, tagOrDigest strin
 	return createdTags, nil
 }
 
+func manifestURLWithTags(repo string, tagOrDigest string, tags []string) string {
+	u := manifestURL(repo, tagOrDigest)
+	if len(tags) == 0 {
+		return u
+	}
+	q := make(url.Values)
+	for _, tag := range tags {
+		q.Add("tag", tag)
+	}
+	return u + "?" + q.Encode()
+}
+
+// CopyImage copies an image from fromRepo into toRepo using reference as the
+// source tag or digest.
+//
+// Experimental: CopyImage uses a registry extension and is not part of
+// [oci.Interface] or the OCI distribution specification.
+func (c *Client) CopyImage(ctx context.Context, fromRepo, toRepo, reference string) (oci.Descriptor, error) {
+	q := url.Values{}
+	q.Set("from", fromRepo)
+	q.Set("reference", reference)
+	req, err := newRequest(ctx, http.MethodPost, copyImageURL(toRepo, q), nil, mountScope(fromRepo, toRepo))
+	if err != nil {
+		return oci.Descriptor{}, err
+	}
+	resp, err := c.do(req, http.StatusCreated)
+	if err != nil {
+		return oci.Descriptor{}, err
+	}
+	resp.Body.Close()
+	return descriptorFromResponse(resp, "", requireDigest)
+}
+
+func copyImageURL(repo string, q url.Values) string {
+	return "/v2/" + repo + "/_docker/copy/image?" + q.Encode()
+}
+
 // MountBlob makes a blob from fromRepo available in toRepo without uploading it again.
 func (c *Client) MountBlob(ctx context.Context, fromRepo, toRepo string, dig oci.Digest) (oci.Descriptor, error) {
 	q := url.Values{}

ociclient/writer_test.go

@@ -0,0 +1,47 @@
+package ociclient
+
+import (
+	"context"
+	"net/http"
+	"testing"
+
+	"github.com/docker/oci"
+	"github.com/docker/oci/ociauth"
+	"github.com/stretchr/testify/require"
+)
+
+func TestCopyImage(t *testing.T) {
+	c, err := New("registry.example", &Options{
+		Transport: transportFunc(func(req *http.Request) (*http.Response, error) {
+			require.Equal(t, http.MethodPost, req.Method)
+			require.Equal(t, "https", req.URL.Scheme)
+			require.Equal(t, "registry.example", req.URL.Host)
+			require.Equal(t, "/v2/dst/repo/_docker/copy/image", req.URL.Path)
+			require.Equal(t, "src/repo", req.URL.Query().Get("from"))
+			require.Equal(t, "stable", req.URL.Query().Get("reference"))
+			require.Nil(t, req.Body)
+			require.Empty(t, req.Header.Get("Content-Type"))
+
+			scope := ociauth.RequestInfoFromContext(req.Context()).RequiredScope
+			require.Equal(t, "repository:dst/repo:pull,push repository:src/repo:pull", scope.Canonical().String())
+
+			return &http.Response{
+				StatusCode: http.StatusCreated,
+				Status:     "201 Created",
+				Header: http.Header{
+					"Content-Type":          {oci.MediaTypeImageManifest},
+					"Docker-Content-Digest": {testDigest.String()},
+				},
+				Body:    http.NoBody,
+				Request: req,
+			}, nil
+		}),
+	})
+	require.NoError(t, err)
+
+	desc, err := c.CopyImage(context.Background(), "src/repo", "dst/repo", "stable")
+	require.NoError(t, err)
+	require.Equal(t, testDigest, desc.Digest)
+	require.Equal(t, oci.MediaTypeImageManifest, desc.MediaType)
+	require.Zero(t, desc.Size)
+}