Finish up parameter parsing and validation.

Login to a docker index now works, ready for
implementation of the actual push logic.

post-processor/docker-push/post-processor.go

 package dockerpush
 
 import (
-	"errors"
-	"github.com/mitchellh/mapstructure"
+	"fmt"
+	"github.com/mitchellh/packer/common"
 	"github.com/mitchellh/packer/packer"
 	"os/exec"
 )
 
 type Config struct {
-	Registry string
-	Username string
-	Password string
-	Email    string
+	common.PackerConfig `mapstructure:",squash"`
+
+	Registry string `mapstructure:"registry"`
+	Username string `mapstructure:"username"`
+	Password string `mapstructure:"password"`
+	Email    string `mapstructure:"email"`
+
+	tpl *packer.ConfigTemplate
 }
 
 type PostProcessor struct {
 	config Config
 }
 
-func (p *PostProcessor) Configure(raw ...interface{}) error {
-	if err := mapstructure.Decode(raw, &p.config); err != nil {
+func (p *PostProcessor) Configure(raws ...interface{}) error {
+	_, err := common.DecodeConfig(&p.config, raws...)
+	if err != nil {
 		return err
 	}
 
-	if p.config.Registry == "" {
-		p.config.Registry = "registry.docker.io"
+	p.config.tpl, err = packer.NewConfigTemplate()
+	if err != nil {
+		return err
+	}
+	p.config.tpl.UserVars = p.config.PackerUserVars
+
+	// Accumulate any errors
+	errs := new(packer.MultiError)
+
+	templates := map[string]*string{
+		"username": &p.config.Username,
+		"password": &p.config.Password,
 	}
 
-	if p.config.Username == "" {
-		return errors.New("Username is required to push docker image")
+	for key, ptr := range templates {
+		if *ptr == "" {
+			errs = packer.MultiErrorAppend(
+				errs, fmt.Errorf("%s must be set", key))
+		}
+
+		*ptr, err = p.config.tpl.Process(*ptr, nil)
+		if err != nil {
+			errs = packer.MultiErrorAppend(
+				errs, fmt.Errorf("Error processing %s: %s", key, err))
+		}
 	}
 
-	if p.config.Password == "" {
-		return errors.New("Password is required to push docker image")
+	if len(errs.Errors) > 0 {
+		return errs
 	}
 
 	return nil
+
 }
 
 func (p *PostProcessor) PostProcess(ui packer.Ui, artifact packer.Artifact) (packer.Artifact, bool, error) {
 	id := artifact.Id()
 	ui.Say("Pushing image: " + id)
 
+	if p.config.Registry == "" {
+
+		if p.config.Email == "" {
+			cmd := exec.Command("docker",
+				"login",
+				"-u="+p.config.Username,
+				"-p="+p.config.Password)
+
+			if err := cmd.Run(); err != nil {
+				ui.Say("Login to the registry " + p.config.Registry + " failed")
+				return nil, false, err
+			}
+
+		} else {
+			cmd := exec.Command("docker",
+				"login",
+				"-u="+p.config.Username,
+				"-p="+p.config.Password,
+				"-e="+p.config.Email)
+
+			if err := cmd.Run(); err != nil {
+				ui.Say("Login to the registry " + p.config.Registry + " failed")
+				return nil, false, err
+			}
+
+		}
+
+	} else {
 		if p.config.Email == "" {
-		cmd := exec.Command("docker", "login",
-			"-u=\""+p.config.Username+"\"",
-			"-p=\""+p.config.Password+"\"")
+			cmd := exec.Command("docker",
+				"login",
+				"-u="+p.config.Username,
+				"-p="+p.config.Password,
+				p.config.Registry)
 
 			if err := cmd.Run(); err != nil {
 				ui.Say("Login to the registry " + p.config.Registry + " failed")
@@ -55,9 +110,10 @@ func (p *PostProcessor) PostProcess(ui packer.Ui, artifact packer.Artifact) (pac
 		} else {
 			cmd := exec.Command("docker",
 				"login",
-			"-u=\""+p.config.Username+"\"",
-			"-p=\""+p.config.Password+"\"",
-			"-e=\""+p.config.Email+"\"")
+				"-u="+p.config.Username,
+				"-p="+p.config.Password,
+				"-e="+p.config.Email,
+				p.config.Registry)
 
 			if err := cmd.Run(); err != nil {
 				ui.Say("Login to the registry " + p.config.Registry + " failed")
@@ -65,6 +121,8 @@ func (p *PostProcessor) PostProcess(ui packer.Ui, artifact packer.Artifact) (pac
 			}
 
 		}
+	}
+
 	cmd := exec.Command("docker", "push", id)
 	if err := cmd.Run(); err != nil {
 		ui.Say("Failed to push image: " + id)