add download support to file provisioner

provisioner/file/provisioner.go

@@ -20,6 +20,9 @@ type Config struct {
 	// The remote path where the local file will be uploaded to.
 	Destination string
 
+	// Direction
+	Direction string
+
 	ctx interpolate.Context
 }
 
@@ -38,12 +41,28 @@ func (p *Provisioner) Prepare(raws ...interface{}) error {
 		return err
 	}
 
+	if p.config.Direction == "" {
+		p.config.Direction = "upload"
+	}
+
 	var errs *packer.MultiError
 	if _, err := os.Stat(p.config.Source); err != nil {
 		errs = packer.MultiErrorAppend(errs,
 			fmt.Errorf("Bad source '%s': %s", p.config.Source, err))
 	}
 
+	if p.config.Direction != "download" && p.config.Direction != "upload" {
+		errs = packer.MultiErrorAppend(errs,
+			errors.New("Direction must be one of: download, upload."))
+	}
+
+	if p.config.Direction == "upload" {
+		if _, err := os.Stat(p.config.Source); err != nil {
+			errs = packer.MultiErrorAppend(errs,
+				fmt.Errorf("Bad source '%s': %s", p.config.Source, err))
+		}
+	}
+
 	if p.config.Destination == "" {
 		errs = packer.MultiErrorAppend(errs,
 			errors.New("Destination must be specified."))
@@ -57,6 +76,30 @@ func (p *Provisioner) Prepare(raws ...interface{}) error {
 }
 
 func (p *Provisioner) Provision(ui packer.Ui, comm packer.Communicator) error {
+	if p.config.Direction == "download" {
+		return p.ProvisionDownload(ui, comm)
+	} else {
+		return p.ProvisionUpload(ui, comm)
+	}
+}
+
+func (p *Provisioner) ProvisionDownload(ui packer.Ui, comm packer.Communicator) error {
+	ui.Say(fmt.Sprintf("Downloading %s => %s", p.config.Source, p.config.Destination))
+
+	f, err := os.OpenFile(p.config.Destination, os.O_CREATE|os.O_WRONLY|os.O_TRUNC, 0644)
+	if err != nil {
+		return err
+	}
+	defer f.Close()
+
+	err = comm.Download(p.config.Source, f)
+	if err != nil {
+		ui.Error(fmt.Sprintf("Download failed: %s", err))
+	}
+	return err
+}
+
+func (p *Provisioner) ProvisionUpload(ui packer.Ui, comm packer.Communicator) error {
 	ui.Say(fmt.Sprintf("Uploading %s => %s", p.config.Source, p.config.Destination))
 	info, err := os.Stat(p.config.Source)
 	if err != nil {