Use a FullName:Tag representation when creating tarballs for (docker …

…load)

This makes the tagging behavior consistent with (docker pull) for
projectatomic/docker, and does not change behavior for docker/docker.

See the added comment, and containers/image#72 ,
for more explanation.

Signed-off-by: Miloslav Trmač <mitr@redhat.com>

docker/daemon/daemon_dest.go

@@ -22,7 +22,8 @@ import (
 )
 
 type daemonImageDestination struct {
-	ref daemonReference
+	ref            daemonReference
+	namedTaggedRef reference.NamedTagged // Strictly speaking redundant with ref above; having the field makes it structurally impossible for later users to fail.
 	// For talking to imageLoadGoroutine
 	goroutineCancel context.CancelFunc
 	statusChannel   <-chan error
@@ -37,7 +38,8 @@ func newImageDestination(systemCtx *types.SystemContext, ref daemonReference) (t
 	if ref.ref == nil {
 		return nil, fmt.Errorf("Invalid destination docker-daemon:%s: a destination must be a name:tag", ref.StringWithinTransport())
 	}
-	if _, ok := ref.ref.(reference.NamedTagged); !ok {
+	namedTaggedRef, ok := ref.ref.(reference.NamedTagged)
+	if !ok {
 		return nil, fmt.Errorf("Invalid destination docker-daemon:%s: a destination must be a name:tag", ref.StringWithinTransport())
 	}
 
@@ -55,6 +57,7 @@ func newImageDestination(systemCtx *types.SystemContext, ref daemonReference) (t
 
 	return &daemonImageDestination{
 		ref:             ref,
+		namedTaggedRef:  namedTaggedRef,
 		goroutineCancel: goroutineCancel,
 		statusChannel:   statusChannel,
 		writer:          writer,
@@ -181,9 +184,28 @@ func (d *daemonImageDestination) PutManifest(m []byte) error {
 	for _, l := range man.Layers {
 		layerPaths = append(layerPaths, l.Digest)
 	}
+
+	// For github.com/docker/docker consumers, this works just as well as
+	//   refString := d.namedTaggedRef.String()  [i.e. d.ref.ref.String()]
+	// because when reading the RepoTags strings, github.com/docker/docker/reference
+	// normalizes both of them to the same value.
+	//
+	// Doing it this way to include the normalized-out `docker.io[/library]` does make
+	// a difference for github.com/projectatomic/docker consumers, with the
+	// “Add --add-registry and --block-registry options to docker daemon” patch.
+	// These consumers treat reference strings which include a hostname and reference
+	// strings without a hostname differently.
+	//
+	// Using the host name here is more explicit about the intent, and it has the same
+	// effect as (docker pull) in projectatomic/docker, which tags the result using
+	// a hostname-qualified reference.
+	// See https://github.com/containers/image/issues/72 for a more detailed
+	// analysis and explanation.
+	refString := fmt.Sprintf("%s:%s", d.namedTaggedRef.FullName(), d.namedTaggedRef.Tag())
+
 	items := []manifestItem{{
 		Config:       man.Config.Digest,
-		RepoTags:     []string{d.ref.ref.String()}, // newImageDestination ensures that d.ref.ref is a reference.NamedTagged
+		RepoTags:     []string{refString},
 		Layers:       layerPaths,
 		Parent:       "",
 		LayerSources: nil,