c8d/container/inspect: Return ImageManifestDescriptor

`ImageManifestDescriptor` will contain an OCI descriptor of
platform-specific manifest of the image that was picked when creating
the container.

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

daemon/inspect.go

@@ -77,11 +77,21 @@ func (daemon *Daemon) ContainerInspect(ctx context.Context, name string, options
 		base.SizeRootFs = &sizeRootFs
 	}
 
+	imageManifest := ctr.ImageManifest
+	if imageManifest != nil && imageManifest.Platform == nil {
+		// Copy the image manifest to avoid mutating the original
+		c := *imageManifest
+		imageManifest = &c
+
+		imageManifest.Platform = &ctr.ImagePlatform
+	}
+
 	return &containertypes.InspectResponse{
-		ContainerJSONBase: base,
-		Mounts:            mountPoints,
-		Config:            ctr.Config,
-		NetworkSettings:   networkSettings,
+		ContainerJSONBase:       base,
+		Mounts:                  mountPoints,
+		Config:                  ctr.Config,
+		NetworkSettings:         networkSettings,
+		ImageManifestDescriptor: imageManifest,
 	}, nil
 }