Add VHD and GCE output formats

- VHD is uncompressed VHD. Currently hard coded at 1GB, which may need to change. Use `format: vhd`
- GCE is the GCE compressed tarred raw image. Use `format: gce-img` - reserving `gce` for actually
  uploading the image.

Signed-off-by: Justin Cormack <justin.cormack@docker.com>

output.go

@@ -11,6 +11,8 @@ import (
 const (
 	bios = "mobylinux/mkimage-iso-bios:489b1f054a77a8f379d0bfc6cd91639b4db6b67c@sha256:0f058951aac4367d132682aa19eeb5cdcb05600a5d51fe5d0fcbd97b03ae4f87"
 	efi  = "mobylinux/mkimage-iso-efi:b210c58e096e53082d35b28fa2b52dba6ae200c8@sha256:10c2789bf5fbd27c35c5fe2f3b97f75a7108bbde389d0f5ed750e3e2dae95376"
+	gce  = "mobylinux/mkimage-gce:2039be4e39e855d1845aee188e266bba3f1d2eed@sha256:e12f76003fd9eaa0c6f39f149db5998cf56de42539b989c994893c8344ca69c0"
+	vhd  = "mobylinux/mkimage-vhd:73c80e433bf717578c507621a84fd58cec27fe95@sha256:0ae1eda2d6592f309977dc4b25cca120cc4e2ee2cc786e88fdc2761c0d49cb14"
 )
 
 func outputs(m *Moby, base string, bzimage []byte, initrd []byte) error {
@@ -31,6 +33,16 @@ func outputs(m *Moby, base string, bzimage []byte, initrd []byte) error {
 			if err != nil {
 				return fmt.Errorf("Error writing %s output: %v", o.Format, err)
 			}
+		case "gce-img":
+			err := outputImg(gce, base+".img.tar.gz", bzimage, initrd, m.Kernel.Cmdline)
+			if err != nil {
+				return fmt.Errorf("Error writing %s output: %v", o.Format, err)
+			}
+		case "vhd":
+			err := outputImg(vhd, base+".vhd", bzimage, initrd, m.Kernel.Cmdline)
+			if err != nil {
+				return fmt.Errorf("Error writing %s output: %v", o.Format, err)
+			}
 		case "":
 			return fmt.Errorf("No format specified for output")
 		default:
@@ -40,9 +52,7 @@ func outputs(m *Moby, base string, bzimage []byte, initrd []byte) error {
 	return nil
 }
 
-// TODO add kernel command line
+func tarInitrdKernel(bzimage, initrd []byte) (*bytes.Buffer, error) {
-func outputISO(image, filename string, bzimage []byte, initrd []byte, args ...string) error {
-	// first build the input tarball from kernel and initrd
 	buf := new(bytes.Buffer)
 	tw := tar.NewWriter(buf)
 	hdr := &tar.Header{
@@ -52,11 +62,11 @@ func outputISO(image, filename string, bzimage []byte, initrd []byte, args ...st
 	}
 	err := tw.WriteHeader(hdr)
 	if err != nil {
-		return err
+		return buf, err
 	}
 	_, err = tw.Write(bzimage)
 	if err != nil {
-		return err
+		return buf, err
 	}
 	hdr = &tar.Header{
 		Name: "initrd.img",
@@ -65,13 +75,38 @@ func outputISO(image, filename string, bzimage []byte, initrd []byte, args ...st
 	}
 	err = tw.WriteHeader(hdr)
 	if err != nil {
-		return err
+		return buf, err
 	}
 	_, err = tw.Write(initrd)
 	if err != nil {
-		return err
+		return buf, err
 	}
 	err = tw.Close()
+	if err != nil {
+		return buf, err
+	}
+	return buf, nil
+}
+
+func outputImg(image, filename string, bzimage []byte, initrd []byte, args ...string) error {
+	buf, err := tarInitrdKernel(bzimage, initrd)
+	if err != nil {
+		return err
+	}
+	img, err := dockerRunInput(buf, append([]string{image}, args...)...)
+	if err != nil {
+		return err
+	}
+	err = ioutil.WriteFile(filename, img, os.FileMode(0644))
+	if err != nil {
+		return err
+	}
+	fmt.Println(filename)
+	return nil
+}
+
+func outputISO(image, filename string, bzimage []byte, initrd []byte, args ...string) error {
+	buf, err := tarInitrdKernel(bzimage, initrd)
 	if err != nil {
 		return err
 	}