[RFC] types: ImageSource: support getting a specific manifest

directory/directory_src.go

@@ -26,7 +26,7 @@ func (s *dirImageSource) IntendedDockerReference() string {
 }
 
 // it's up to the caller to determine the MIME type of the returned manifest's bytes
-func (s *dirImageSource) GetManifest(_ []string) ([]byte, string, error) {
+func (s *dirImageSource) GetManifest(_ []string, _ string) ([]byte, string, error) {
 	m, err := ioutil.ReadFile(manifestPath(s.dir))
 	if err != nil {
 		return nil, "", err

directory/directory_test.go

@@ -27,7 +27,7 @@ func TestGetPutManifest(t *testing.T) {
 	assert.NoError(t, err)
 
 	src := NewDirImageSource(tmpDir)
-	m, mt, err := src.GetManifest(nil)
+	m, mt, err := src.GetManifest(nil, "")
 	assert.NoError(t, err)
 	assert.Equal(t, man, m)
 	assert.Equal(t, "", mt)

docker/docker_image_src.go

@@ -71,8 +71,11 @@ func simplifyContentType(contentType string) string {
 	return mimeType
 }
 
-func (s *dockerImageSource) GetManifest(mimetypes []string) ([]byte, string, error) {
-	url := fmt.Sprintf(manifestURL, s.ref.RemoteName(), s.tag)
+func (s *dockerImageSource) GetManifest(mimetypes []string, reference string) ([]byte, string, error) {
+	if reference == "" {
+		reference = s.tag
+	}
+	url := fmt.Sprintf(manifestURL, s.ref.RemoteName(), reference)
 	// TODO(runcom) set manifest version header! schema1 for now - then schema2 etc etc and v1
 	// TODO(runcom) NO, switch on the resulter manifest like Docker is doing
 	headers := make(map[string][]string)

image/image.go

@@ -52,7 +52,10 @@ func (i *genericImage) IntendedDockerReference() string {
 // NOTE: It is essential for signature verification that Manifest returns the manifest from which BlobDigests is computed.
 func (i *genericImage) Manifest() ([]byte, string, error) {
 	if i.cachedManifest == nil {
-		m, mt, err := i.src.GetManifest([]string{manifest.DockerV2Schema1SignedMIMEType, manifest.DockerV2Schema1MIMEType})
+		m, mt, err := i.src.GetManifest([]string{
+			manifest.DockerV2Schema1SignedMIMEType,
+			manifest.DockerV2Schema1MIMEType,
+		}, "")
 		if err != nil {
 			return nil, "", err
 		}

openshift/openshift.go

@@ -193,11 +193,11 @@ func (s *openshiftImageSource) IntendedDockerReference() string {
 	return s.client.canonicalDockerReference()
 }
 
-func (s *openshiftImageSource) GetManifest(mimetypes []string) ([]byte, string, error) {
+func (s *openshiftImageSource) GetManifest(mimetypes []string, reference string) ([]byte, string, error) {
 	if err := s.ensureImageIsResolved(); err != nil {
 		return nil, "", err
 	}
-	return s.docker.GetManifest(mimetypes)
+	return s.docker.GetManifest(mimetypes, reference)
 }
 
 func (s *openshiftImageSource) GetBlob(digest string) (io.ReadCloser, int64, error) {

types/types.go

@@ -14,8 +14,9 @@ type ImageSource interface {
 	// May be "" if unknown.
 	IntendedDockerReference() string
 	// GetManifest returns the image's manifest along with its MIME type. The empty string is returned if the MIME type is unknown. The slice parameter indicates the supported mime types the manifest should be when getting it.
+	// The string parameter indicates the reference to be looking for when getting a manifest.
 	// It may use a remote (= slow) service.
-	GetManifest([]string) ([]byte, string, error)
+	GetManifest([]string, string) ([]byte, string, error)
 	// Note: Calling GetBlob() may have ordering dependencies WRT other methods of this type. FIXME: How does this work with (docker save) on stdin?
 	// the second return value is the size of the blob. If not known 0 is returned
 	GetBlob(digest string) (io.ReadCloser, int64, error)