feat: support mounting blobs during copy

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

@@ -17,6 +17,7 @@
 
 import (
 	"context"
+	"errors"
 	"io"
 	"os"
 
@@ -66,6 +67,14 @@
 	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 {
+	if mounter, ok := t.GraphTarget.(registry.Mounter); ok {
+		return mounter.Mount(ctx, desc, fromRepo, getContent)
+	}
+	return errors.New("not implemented")
+}
+
 // 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/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)
 	}