Add simple init command

command/init.go

@@ -0,0 +1,75 @@
+package command
+
+import (
+	"context"
+	"fmt"
+
+	"github.com/hashicorp/packer/version"
+)
+
+// InitCommand initializes a Packer working directory.
+type InitCommand struct {
+	Meta
+}
+
+func (c *InitCommand) Run(args []string) int {
+	ctx, cleanup := handleTermInterrupt(c.Ui)
+	defer cleanup()
+
+	cla, ret := c.ParseArgs(args)
+	if ret != 0 {
+		return ret
+	}
+
+	return c.RunContext(ctx, cla)
+}
+
+func (c *InitCommand) ParseArgs(args []string) (*InitArgs, int) {
+	var cfg InitArgs
+	flags := c.Meta.FlagSet("init", FlagSetNone)
+	flags.Usage = func() { c.Ui.Say(c.Help()) }
+	cfg.AddFlagSets(flags)
+	if err := flags.Parse(args); err != nil {
+		return &cfg, 1
+	}
+
+	return &cfg, 0
+}
+
+func (c *InitCommand) RunContext(ctx context.Context, cla *InitArgs) int {
+	fmt.Printf(`%s
+
+Packer initialized in an empty directory!
+
+The directory has no Packer templates. You may begin working
+with Packer immediately by creating a Packer template.
+`, version.FormattedVersion())
+
+	return 0
+}
+
+func (c *InitCommand) Help() string {
+	helpText := `
+Usage: packer init [options]
+
+  Initialize a new or existing Packer working directory by downloading
+  builders, provisioners, and post-processors defined in the template.
+
+  This is the first command that should be executed when working with a new
+  or existing template. Running this command in an empty directory will
+  will perform no operation, and will need to be executed once a template
+  has been added to the directory to initialize the working directory.
+
+  It is safe to run init multiple times within a given directory.
+`
+	return helpText
+
+}
+
+type InitArgs struct {
+	MetaArgs
+}
+
+func (c *InitCommand) Synopsis() string {
+	return "Initializes a Packer working directory"
+}

commands.go

@@ -64,5 +64,11 @@ func init() {
 				Meta: *CommandMeta,
 			}, nil
 		},
+
+		"init": func() (cli.Command, error) {
+			return &command.InitCommand{
+				Meta: *CommandMeta,
+			}, nil
+		},
 	}
 }