feat: support mounting blobs during copy

cmd/oras/internal/display/track/target.go

@@ -66,6 +66,13 @@ func NewTarget(t oras.GraphTarget, actionPrompt, donePrompt string, tty *os.File
 	return gt, nil
 }
 
+// Mount makes graphTarget implement oras.Mounter.
+func (t *graphTarget) Mount(ctx context.Context, desc ocispec.Descriptor, fromRepo string, getContent func() (io.ReadCloser, error)) error {
+	// should not be called if the underlying GraphTarget is not a mounter
+	mounter := t.GraphTarget.(registry.Mounter)
+	return mounter.Mount(ctx, desc, fromRepo, getContent)
+}
+
 // Push pushes the content to the base oras.GraphTarget with tracking.
 func (t *graphTarget) Push(ctx context.Context, expected ocispec.Descriptor, content io.Reader) error {
 	r, err := managedReader(content, expected, t.manager, t.actionPrompt, t.donePrompt)

cmd/oras/internal/display/track/target_test.go

@@ -25,6 +25,7 @@ import (
 	ocispec "github.com/opencontainers/image-spec/specs-go/v1"
 	"oras.land/oras-go/v2"
 	"oras.land/oras-go/v2/content/memory"
+	"oras.land/oras-go/v2/registry/remote"
 	"oras.land/oras/cmd/oras/internal/display/console/testutils"
 )
 
@@ -79,34 +80,7 @@ func Test_referenceGraphTarget_PushReference(t *testing.T) {
 	}
 }
 
-func Test_referenceGraphTarget_Prompt(t *testing.T) {
-	// prepare
-	pty, device, err := testutils.NewPty()
-	if err != nil {
-		t.Fatal(err)
-	}
-	defer device.Close()
-	content := []byte("test")
-	desc := ocispec.Descriptor{
-		MediaType: "application/octet-stream",
-		Digest:    digest.FromBytes(content),
-		Size:      int64(len(content)),
-	}
-	// test
-	prompt := "prompt"
-	target, err := NewTarget(memory.New(), "action", "done", device)
-	if err != nil {
-		t.Fatal(err)
-	}
-	m := target.(*graphTarget).manager
-	if err := target.Prompt(desc, prompt); err != nil {
-		t.Fatal(err)
-	}
-	if err := m.Close(); err != nil {
-		t.Fatal(err)
-	}
-	// validate
-	if err = testutils.MatchPty(pty, device, prompt, desc.MediaType, "100.00%", desc.Digest.String()); err != nil {
-		t.Fatal(err)
-	}
+func Test_referenceGraphTarget_Mount(t *testing.T) {
+	target := graphTarget{GraphTarget: &remote.Repository{}}
+	_ = target.Mount(context.Background(), ocispec.Descriptor{}, "", nil)
 }

cmd/oras/root/cp.go

@@ -29,6 +29,7 @@
 	"oras.land/oras-go/v2"
 	"oras.land/oras-go/v2/content"
 	"oras.land/oras-go/v2/registry"
+	"oras.land/oras-go/v2/registry/remote"
 	"oras.land/oras-go/v2/registry/remote/auth"
 	"oras.land/oras/cmd/oras/internal/argument"
 	"oras.land/oras/cmd/oras/internal/display"
@@ -162,8 +163,15 @@
 		promptCopying = "Copying"
 		promptCopied  = "Copied "
 		promptSkipped = "Skipped"
+		promptMounted = "Mounted"
 	)
-
+	srcRepo, srcIsRemote := src.(*remote.Repository)
+	dstRepo, dstIsRemote := dst.(*remote.Repository)
+	if srcIsRemote && dstIsRemote && srcRepo.Reference.Registry == dstRepo.Reference.Registry {
+		extendedCopyOptions.MountFrom = func(ctx context.Context, desc ocispec.Descriptor) ([]string, error) {
+			return []string{srcRepo.Reference.Repository}, nil
+		}
+	}
 	if opts.TTY == nil {
 		// none TTY output
 		extendedCopyOptions.OnCopySkipped = func(ctx context.Context, desc ocispec.Descriptor) error {
@@ -180,6 +188,10 @@
 			}
 			return display.PrintStatus(desc, promptCopied, opts.Verbose)
 		}
+		extendedCopyOptions.OnMounted = func(ctx context.Context, desc ocispec.Descriptor) error {
+			committed.Store(desc.Digest.String(), desc.Annotations[ocispec.AnnotationTitle])
+			return display.PrintStatus(desc, promptMounted, opts.Verbose)
+		}
 	} else {
 		// TTY output
 		tracked, err := track.NewTarget(dst, promptCopying, promptCopied, opts.TTY)
@@ -198,6 +210,10 @@
 				return tracked.Prompt(desc, promptSkipped)
 			})
 		}
+		extendedCopyOptions.OnMounted = func(ctx context.Context, desc ocispec.Descriptor) error {
+			committed.Store(desc.Digest.String(), desc.Annotations[ocispec.AnnotationTitle])
+			return tracked.Prompt(desc, promptMounted)
+		}
 	}
 
 	var desc ocispec.Descriptor

go.mod

@@ -14,7 +14,7 @@ require (
 	golang.org/x/sync v0.6.0
 	golang.org/x/term v0.16.0
 	gopkg.in/yaml.v3 v3.0.1
-	oras.land/oras-go/v2 v2.3.1-0.20231227022511-1d9ad6c409b3
+	oras.land/oras-go/v2 v2.3.1-0.20240111050452-3b1dd0e97000
 )
 
 require (

go.sum

@@ -41,3 +41,5 @@ gopkg.in/yaml.v3 v3.0.1 h1:fxVm/GzAzEWqLHuvctI91KS9hhNmmWOoWu0XTYJS7CA=
 gopkg.in/yaml.v3 v3.0.1/go.mod h1:K4uyk7z7BCEPqu6E+C64Yfv1cQ7kz7rIZviUmN+EgEM=
 oras.land/oras-go/v2 v2.3.1-0.20231227022511-1d9ad6c409b3 h1:cF1ErV93cAw4i5/MNF4pW6ULHa27ig3oYGlxouzymY8=
 oras.land/oras-go/v2 v2.3.1-0.20231227022511-1d9ad6c409b3/go.mod h1:W2rj9/rGtsTh9lmU3S0uq3iwvR6wNvUuD8nmOFmWBUY=
+oras.land/oras-go/v2 v2.3.1-0.20240111050452-3b1dd0e97000 h1:tCh6spxJeREZx+phlJMk76/gcK3V02g56siet4NP180=
+oras.land/oras-go/v2 v2.3.1-0.20240111050452-3b1dd0e97000/go.mod h1:JE7nRv2IHCiuu7kbH3UmDCp7bYD38yfnt1sl0lkLrwk=

test/e2e/internal/utils/match/status.go

@@ -76,6 +76,7 @@ func newStateMachine(cmd string) *stateMachine {
 		sm.addPath("Copying", "Copied")
 		sm.addPath("Skipped")
 		sm.addPath("Exists")
+		sm.addPath("Mounted")
 	default:
 		ginkgo.Fail("Unrecognized cmd name " + cmd)
 	}

test/e2e/suite/command/cp.go

@@ -349,6 +349,15 @@ var _ = Describe("1.1 registry users:", func() {
 
 var _ = Describe("OCI spec 1.0 registry users:", func() {
 	When("running `cp`", func() {
+		It("should copy an image artifact with mounting", func() {
+			repo := cpTestRepo("1.0-mount")
+			src := RegistryRef(FallbackHost, ArtifactRepo, foobar.Tag)
+			dst := RegistryRef(FallbackHost, repo, "")
+			out := ORAS("cp", src, dst, "-v").Exec()
+			Expect(out).Should(gbytes.Say("Mounted fcde2b2edba5 bar"))
+			CompareRef(src, RegistryRef(FallbackHost, repo, foobar.Digest))
+		})
+
 		It("should copy an image artifact and its referrers from a registry to a fallback registry", func() {
 			repo := cpTestRepo("to-fallback")
 			stateKeys := append(append(foobar.ImageLayerStateKeys, foobar.ManifestStateKey, foobar.ImageReferrerConfigStateKeys[0]), foobar.ImageReferrersStateKeys...)