First cut at vagrant post-processor for docker

Vagrantfile

@@ -5,6 +5,10 @@ LINUX_BASE_BOX = "bento/ubuntu-16.04"
 FREEBSD_BASE_BOX = "jen20/FreeBSD-12.0-CURRENT"
 
 Vagrant.configure(2) do |config|
+        if Vagrant.has_plugin?("vagrant-cachier")
+                config.cache.scope = :box
+        end
+
 	# Compilation and development boxes
 	config.vm.define "linux", autostart: true, primary: true do |vmCfg|
 		vmCfg.vm.box = LINUX_BASE_BOX

post-processor/vagrant/docker.go

@@ -0,0 +1,26 @@
+package vagrant
+
+import (
+	"fmt"
+
+	"github.com/hashicorp/packer/packer"
+)
+
+type DockerProvider struct{}
+
+func (p *DockerProvider) KeepInputArtifact() bool {
+	return false
+}
+
+func (p *DockerProvider) Process(ui packer.Ui, artifact packer.Artifact, dir string) (vagrantfile string, metadata map[string]interface{}, err error) {
+	// Create the metadata
+	metadata = map[string]interface{}{"provider": "docker"}
+
+	vagrantfile = fmt.Sprintf(dockerVagrantfile)
+	return
+}
+
+var dockerVagrantfile = `
+Vagrant.configure("2") do |config|
+end
+`

post-processor/vagrant/docker_test.go

@@ -0,0 +1,9 @@
+package vagrant
+
+import (
+	"testing"
+)
+
+func TestDockerProvider_impl(t *testing.T) {
+	var _ Provider = new(DockerProvider)
+}

post-processor/vagrant/post-processor.go

@@ -31,6 +31,7 @@ var builtins = map[string]string{
 	"MSOpenTech.hyperv":                   "hyperv",
 	"transcend.qemu":                      "libvirt",
 	"ustream.lxc":                         "lxc",
+	"packer.post-processor.docker-import": "docker",
 }
 
 type Config struct {
@@ -241,6 +242,8 @@ func providerForName(name string) Provider {
 		return new(GoogleProvider)
 	case "lxc":
 		return new(LXCProvider)
+	case "docker":
+		return new(DockerProvider)
 	default:
 		return nil
 	}