imagebuildah: add AdditionalTags

Add an AdditionalTags field to the imagebuildah options structure, to
provide for additional tags which we'll want to apply to the image that
we're writing.

Signed-off-by: Nalin Dahyabhai <nalin@redhat.com>

Closes: #88
Approved by: rhatdan

commit.go

@@ -1,8 +1,12 @@
 package buildah
 
 import (
+	"fmt"
+
 	"github.com/containers/image/copy"
+	"github.com/containers/image/docker/reference"
 	"github.com/containers/image/signature"
+	"github.com/containers/image/storage"
 	"github.com/containers/image/types"
 	"github.com/containers/storage/pkg/archive"
 )
@@ -19,10 +23,32 @@ type CommitOptions struct {
 	// specified, indicating that the shared, system-wide default policy
 	// should be used.
 	SignaturePolicyPath string
+	// AdditionalTags is a list of additional names to add to the image, if
+	// the transport to which we're writing the image gives us a way to add
+	// them.
+	AdditionalTags []string
+}
+
+func expandTags(tags []string) ([]string, error) {
+	expanded := []string{}
+	for _, tag := range tags {
+		name, err := reference.ParseNormalizedNamed(tag)
+		if err != nil {
+			return nil, fmt.Errorf("error parsing tag %q: %v", tag, err)
+		}
+		name = reference.TagNameOnly(name)
+		tag = ""
+		if tagged, ok := name.(reference.NamedTagged); ok {
+			tag = ":" + tagged.Tag()
+		}
+		expanded = append(expanded, name.Name()+tag)
+	}
+	return expanded, nil
 }
 
 // Commit writes the contents of the container, along with its updated
-// configuration, to a new image in the specified location.
+// configuration, to a new image in the specified location, and if we know how,
+// add any additional tags that were specified.
 func (b *Builder) Commit(dest types.ImageReference, options CommitOptions) error {
 	policy, err := signature.DefaultPolicy(getSystemContext(options.SignaturePolicyPath))
 	if err != nil {
@@ -37,5 +63,20 @@ func (b *Builder) Commit(dest types.ImageReference, options CommitOptions) error
 		return err
 	}
 	err = copy.Image(policyContext, dest, src, getCopyOptions())
+	switch dest.Transport().Name() {
+	case storage.Transport.Name():
+		tags, err := expandTags(options.AdditionalTags)
+		if err != nil {
+			return err
+		}
+		img, err := storage.Transport.GetStoreImage(b.store, dest)
+		if err != nil {
+			return err
+		}
+		err = b.store.SetNames(img.ID, append(img.Names, tags...))
+		if err != nil {
+			return fmt.Errorf("error setting image names to %v: %v", append(img.Names, tags...), err)
+		}
+	}
 	return err
 }