packer: Start pulling out the global config stuff

command/build/command.go

@@ -49,5 +49,5 @@ func (Command) Run(env packer.Environment, args []string) int {
 }
 
 func (Command) Synopsis() string {
-	return "build image(s) from tempate"
+	return "build image(s) from template"
 }

config.go

+package main
+
+import (
+	"fmt"
+	"github.com/mitchellh/packer/packer"
+	"github.com/mitchellh/packer/packer/plugin"
+	"log"
+	"os/exec"
+)
+
+type config struct {
+	builds map[string]string
+	commands map[string]string
+}
+
+func defaultConfig() (result *config) {
+	commands := []string{"build"}
+
+	result = new(config)
+	result.builds = make(map[string]string)
+	result.commands = make(map[string]string)
+
+	for _, name := range commands {
+		result.commands[name] = fmt.Sprintf("packer-command-%s", name)
+	}
+
+	return
+}
+
+func (c *config) Commands() (result []string) {
+	result = make([]string, 0, len(c.commands))
+	for name, _ := range c.commands {
+		result = append(result, name)
+	}
+	return
+}
+
+func (c *config) LoadCommand(name string) (packer.Command, error) {
+	log.Printf("Loading command: %s\n", name)
+	commandBin, ok := c.commands[name]
+	if !ok {
+		log.Printf("Command not found: %s\n", name)
+		return nil, nil
+	}
+
+	return plugin.Command(exec.Command(commandBin))
+}

packer.go

@@ -8,7 +8,6 @@ import (
 	"io/ioutil"
 	"log"
 	"os"
-	"os/exec"
 )
 
 func main() {
@@ -22,27 +21,10 @@ func main() {
 
 	defer plugin.CleanupClients()
 
-	commands := map[string]string {
-		"build": "packer-build",
-	}
-
-	commandKeys := make([]string, 0, len(commands))
-	for k, _ := range commands {
-		commandKeys = append(commandKeys, k)
-	}
-
+	config := defaultConfig()
 	envConfig := packer.DefaultEnvironmentConfig()
-	envConfig.Commands = commandKeys
-	envConfig.CommandFunc = func(n string) (packer.Command, error) {
-		log.Printf("Loading command: %s\n", n)
-		commandBin, ok := commands[n]
-		if !ok {
-			log.Printf("Command not found: %s\n", n)
-			return nil, nil
-		}
-
-		return plugin.Command(exec.Command(commandBin))
-	}
+	envConfig.Commands = config.Commands()
+	envConfig.CommandFunc = config.LoadCommand
 
 	env, err := packer.NewEnvironment(envConfig)
 	if err != nil {

packer/environment.go

@@ -153,6 +153,8 @@ func (e *coreEnvironment) printHelp() {
 		command, err := e.commandFunc(key)
 		if err != nil {
 			synopsis = fmt.Sprintf("Error loading command: %s", err.Error())
+		} else if command == nil {
+			continue
 		} else {
 			synopsis = command.Synopsis()
 		}

plugin/command-build/Makefile

 plugin:
 	go get -d -v ./...
-	go build -v -o $(ROOTDIR)/bin/packer-build
+	go build -v -o $(ROOTDIR)/bin/packer-command-build
 
 format:
 	go fmt ./...