builder/digitalocean: use DigitalOcean image ID for artifact Id().

builder/digitalocean/artifact.go

@@ -3,6 +3,7 @@ package digitalocean
 import (
 	"fmt"
 	"log"
+	"strconv"
 )
 
 type Artifact struct {
@@ -29,8 +30,7 @@ func (*Artifact) Files() []string {
 }
 
 func (a *Artifact) Id() string {
-	// mimicing the aws builder
-	return fmt.Sprintf("%s:%s", a.regionName, a.snapshotName)
+	return strconv.FormatUint(uint64(a.snapshotId), 10)
 }
 
 func (a *Artifact) String() string {

builder/digitalocean/artifact_test.go

 package digitalocean
 
 import (
-	"github.com/mitchellh/packer/packer"
 	"testing"
+
+	"github.com/mitchellh/packer/packer"
 )
 
 func TestArtifact_Impl(t *testing.T) {
@@ -13,6 +14,15 @@ func TestArtifact_Impl(t *testing.T) {
 	}
 }
 
+func TestArtifactId(t *testing.T) {
+	a := &Artifact{"packer-foobar", 42, "San Francisco", nil}
+	expected := "42"
+
+	if a.Id() != expected {
+		t.Fatalf("artifact ID should match: %v", expected)
+	}
+}
+
 func TestArtifactString(t *testing.T) {
 	a := &Artifact{"packer-foobar", 42, "San Francisco", nil}
 	expected := "A snapshot was created: 'packer-foobar' in region 'San Francisco'"