Split dockerImage to genericImage and docker.Image

The code not dependent on specifics of DockerImageSource now lives in
docker.genericImage; the rest directly in docker.Image.

docker.Image remains the only implementation of types.Image at this
point, but that will change.

docker/docker_image.go

@@ -8,6 +8,12 @@ import (
 	"github.com/projectatomic/skopeo/types"
 )
 
+// Image is a Docker-specific implementation of types.Image with a few extra methods
+// which are specific to Docker.
+type Image struct {
+	genericImage
+}
+
 // NewDockerImage returns a new Image interface type after setting up
 // a client to the registry hosting the given image.
 func NewDockerImage(img, certPath string, tlsVerify bool) (types.Image, error) {
@@ -15,20 +21,20 @@ func NewDockerImage(img, certPath string, tlsVerify bool) (types.Image, error) {
 	if err != nil {
 		return nil, err
 	}
-	return &dockerImage{src: s}, nil
+	return &Image{genericImage{src: s}}, nil
 }
 
 // SourceRefFullName returns a fully expanded name for the repository this image is in.
-func (i *dockerImage) SourceRefFullName() (string, error) {
+func (i *Image) SourceRefFullName() (string, error) {
 	// FIXME? Breaking the abstraction.
-	return i.src.ref.FullName(), nil
+	return i.genericImage.src.ref.FullName(), nil
 }
 
 // GetRepositoryTags list all tags available in the repository. Note that this has no connection with the tag(s) used for this specific image, if any.
-func (i *dockerImage) GetRepositoryTags() ([]string, error) {
+func (i *Image) GetRepositoryTags() ([]string, error) {
 	// FIXME? Breaking the abstraction.
-	url := fmt.Sprintf(tagsURL, i.src.ref.RemoteName())
-	res, err := i.src.c.makeRequest("GET", url, nil, nil)
+	url := fmt.Sprintf(tagsURL, i.genericImage.src.ref.RemoteName())
+	res, err := i.genericImage.src.c.makeRequest("GET", url, nil, nil)
 	if err != nil {
 		return nil, err
 	}

docker/image.go

@@ -18,7 +18,8 @@ var (
 	validHex = regexp.MustCompile(`^([a-f0-9]{64})$`)
 )
 
-type dockerImage struct {
+// genericImage is a general set of utilities for working with container images.
+type genericImage struct {
 	src              *dockerImageSource
 	cachedManifest   []byte   // Private cache for Manifest(); nil if not yet known.
 	cachedSignatures [][]byte // Private cache for Signatures(); nil if not yet known.
@@ -27,12 +28,12 @@ type dockerImage struct {
 // IntendedDockerReference returns the full, unambiguous, Docker reference for this image, _as specified by the user_
 // (not as the image itself, or its underlying storage, claims).  This can be used e.g. to determine which public keys are trusted for this image.
 // May be "" if unknown.
-func (i *dockerImage) IntendedDockerReference() string {
+func (i *genericImage) IntendedDockerReference() string {
 	return i.src.IntendedDockerReference()
 }
 
 // Manifest is like ImageSource.GetManifest, but the result is cached; it is OK to call this however often you need.
-func (i *dockerImage) Manifest() ([]byte, error) {
+func (i *genericImage) Manifest() ([]byte, error) {
 	if i.cachedManifest == nil {
 		m, _, err := i.src.GetManifest([]string{utils.DockerV2Schema1MIMEType})
 		if err != nil {
@@ -44,7 +45,7 @@ func (i *dockerImage) Manifest() ([]byte, error) {
 }
 
 // Signatures is like ImageSource.GetSignatures, but the result is cached; it is OK to call this however often you need.
-func (i *dockerImage) Signatures() ([][]byte, error) {
+func (i *genericImage) Signatures() ([][]byte, error) {
 	if i.cachedSignatures == nil {
 		sigs, err := i.src.GetSignatures()
 		if err != nil {
@@ -55,7 +56,7 @@ func (i *dockerImage) Signatures() ([][]byte, error) {
 	return i.cachedSignatures, nil
 }
 
-func (i *dockerImage) Inspect() (*types.ImageInspectInfo, error) {
+func (i *genericImage) Inspect() (*types.ImageInspectInfo, error) {
 	// TODO(runcom): unused version param for now, default to docker v2-1
 	m, err := i.getSchema1Manifest()
 	if err != nil {
@@ -98,7 +99,7 @@ type v1Image struct {
 }
 
 // TODO(runcom)
-func (i *dockerImage) DockerTar() ([]byte, error) {
+func (i *genericImage) DockerTar() ([]byte, error) {
 	return nil, nil
 }
 
@@ -137,7 +138,7 @@ func sanitize(s string) string {
 	return strings.Replace(s, "/", "-", -1)
 }
 
-func (i *dockerImage) getSchema1Manifest() (manifest, error) {
+func (i *genericImage) getSchema1Manifest() (manifest, error) {
 	manblob, err := i.Manifest()
 	if err != nil {
 		return nil, err
@@ -159,7 +160,7 @@ func (i *dockerImage) getSchema1Manifest() (manifest, error) {
 	return mschema1, nil
 }
 
-func (i *dockerImage) Layers(layers ...string) error {
+func (i *genericImage) Layers(layers ...string) error {
 	m, err := i.getSchema1Manifest()
 	if err != nil {
 		return err
@@ -190,7 +191,7 @@ func (i *dockerImage) Layers(layers ...string) error {
 	return nil
 }
 
-func (i *dockerImage) getLayer(dest types.ImageDestination, digest string) error {
+func (i *genericImage) getLayer(dest types.ImageDestination, digest string) error {
 	stream, err := i.src.GetLayer(digest)
 	if err != nil {
 		return err

types/types.go

@@ -61,6 +61,7 @@ type Image interface {
 	Layers(layers ...string) error // configure download directory? Call it DownloadLayers?
 	// SourceRefFullName returns a fully expanded name for the repository this image is in.
 	SourceRefFullName() (string, error)
+	// Inspect returns various information for (skopeo inspect) parsed from the manifest and configuration.
 	Inspect() (*ImageInspectInfo, error)
 	DockerTar() ([]byte, error) // ??? also, configure output directory
 	// GetRepositoryTags list all tags available in the repository. Note that this has no connection with the tag(s) used for this specific image, if any.