func tagReferenceToTagEvent(stream *api.ImageStream, tagRef api.TagReference, tagOrID string) (*api.TagEvent, error) {
	switch tagRef.From.Kind {
	case "DockerImage":
		return &api.TagEvent{
			Created:              util.Now(),
			DockerImageReference: tagRef.From.Name,
		}, nil

	case "ImageStreamImage":
		ref, err := api.DockerImageReferenceForStream(stream)
		if err != nil {
			return nil, err
		}

		resolvedIDs := api.ResolveImageID(stream, tagOrID)
		switch len(resolvedIDs) {
		case 1:
			ref.ID = resolvedIDs.List()[0]
			return &api.TagEvent{
				Created:              util.Now(),
				DockerImageReference: ref.String(),
				Image:                ref.ID,
			}, nil
		case 0:
			return nil, fmt.Errorf("no images match the prefix %q", tagOrID)
		default:
			return nil, fmt.Errorf("multiple images match the prefix %q: %s", tagOrID, strings.Join(resolvedIDs.List(), ", "))
		}
	case "ImageStreamTag":
		return api.LatestTaggedImage(stream, tagOrID), nil
	default:
		return nil, fmt.Errorf("invalid from.kind %q: it must be ImageStreamImage or ImageStreamTag", tagRef.From.Kind)
	}
}
// resolveImageStreamReference looks up the ImageStream[Tag/Image] and converts it to a
// docker pull spec that can be used in an Image field.
func (g *BuildGenerator) resolveImageStreamReference(ctx kapi.Context, from *kapi.ObjectReference, defaultNamespace string) (string, error) {
	var namespace string
	if len(from.Namespace) != 0 {
		namespace = from.Namespace
	} else {
		namespace = defaultNamespace
	}

	glog.V(4).Infof("Resolving ImageStreamReference %s of Kind %s in namespace %s", from.Name, from.Kind, namespace)
	switch from.Kind {
	case "ImageStream":
		// NOTE: The 'ImageStream' reference should be used only for the 'output' image
		is, err := g.Client.GetImageStream(kapi.WithNamespace(ctx, namespace), from.Name)
		if err != nil {
			glog.V(2).Infof("Error getting ImageStream %s/%s: %v", namespace, from.Name, err)
			return "", err
		}
		image, err := imageapi.DockerImageReferenceForStream(is)
		if err != nil {
			glog.V(2).Infof("Error resolving Docker image reference for %s/%s: %v", namespace, from.Name, err)
			return "", err
		}
		return image.String(), nil
	case "ImageStreamImage":
		imageStreamImage, err := g.Client.GetImageStreamImage(kapi.WithNamespace(ctx, namespace), from.Name)
		if err != nil {
			glog.V(2).Infof("Error ImageStreamReference %s in namespace %s: %v", from.Name, namespace, err)
			if errors.IsNotFound(err) {
				return "", err
			}
			return "", fatalError{err}
		}
		image := imageStreamImage.Image
		glog.V(4).Infof("Resolved ImageStreamReference %s to image %s with reference %s in namespace %s", from.Name, image.Name, image.DockerImageReference, namespace)
		return image.DockerImageReference, nil
	case "ImageStreamTag":
		imageStreamTag, err := g.Client.GetImageStreamTag(kapi.WithNamespace(ctx, namespace), from.Name)
		if err != nil {
			glog.V(2).Infof("Error resolving ImageStreamTag reference %s in namespace %s: %v", from.Name, namespace, err)
			if errors.IsNotFound(err) {
				return "", err
			}
			return "", fatalError{err}
		}
		image := imageStreamTag.Image
		glog.V(4).Infof("Resolved ImageStreamTag %s to image %s with reference %s in namespace %s", from.Name, image.Name, image.DockerImageReference, namespace)
		return image.DockerImageReference, nil
	case "DockerImage":
		return from.Name, nil
	default:
		return "", fatalError{fmt.Errorf("Unknown From Kind %s", from.Kind)}
	}
}