Fix a problem preventing `tag` or `save` from docker-tag artifacts

post-processor/docker-save/post-processor.go

@@ -9,6 +9,7 @@ import (
 	"github.com/mitchellh/packer/helper/config"
 	"github.com/mitchellh/packer/packer"
 	"github.com/mitchellh/packer/post-processor/docker-import"
+	"github.com/mitchellh/packer/post-processor/docker-tag"
 	"github.com/mitchellh/packer/template/interpolate"
 )
 
@@ -44,7 +45,8 @@ func (p *PostProcessor) Configure(raws ...interface{}) error {
 }
 
 func (p *PostProcessor) PostProcess(ui packer.Ui, artifact packer.Artifact) (packer.Artifact, bool, error) {
-	if artifact.BuilderId() != dockerimport.BuilderId {
+	if artifact.BuilderId() != dockerimport.BuilderId &&
+		artifact.BuilderId() != dockertag.BuilderId {
 		err := fmt.Errorf(
 			"Unknown artifact type: %s\nCan only save Docker builder artifacts.",
 			artifact.BuilderId())

post-processor/docker-tag/post-processor.go

@@ -45,7 +45,8 @@ func (p *PostProcessor) Configure(raws ...interface{}) error {
 }
 
 func (p *PostProcessor) PostProcess(ui packer.Ui, artifact packer.Artifact) (packer.Artifact, bool, error) {
-	if artifact.BuilderId() != dockerimport.BuilderId {
+	if artifact.BuilderId() != BuilderId &&
+		artifact.BuilderId() != dockerimport.BuilderId {
 		err := fmt.Errorf(
 			"Unknown artifact type: %s\nCan only tag from Docker builder artifacts.",
 			artifact.BuilderId())