func RebuildOpenShiftImage(name string) error {
	tmpDir, err := ioutils.TempDir("", "otp-rebuild-")
	if err != nil {
		return err
	}
	defer os.RemoveAll(tmpDir)
	if err := pullIfNotExists(name); err != nil {
		return err
	}
	if err := locateAndCopyOpenShiftBinary(tmpDir); err != nil {
		return err
	}
	layerID, err := findBinaryCopyLayer(name)
	if err != nil {
		return err
	}
	tmpBaseImageName := fmt.Sprintf("base-%d", time.Now().Unix())
	util.Debugf("tagging image %q as %q", layerID, tmpBaseImageName)
	if out, err := exec.Command("docker", "tag", layerID, tmpBaseImageName).Output(); err != nil {
		return fmt.Errorf("%s (%v)", string(out), err)
	}
	if err := generateDockerfile(tmpBaseImageName, tmpDir); err != nil {
		return err
	}
	if err := rebuildImage(tmpBaseImageName, name, tmpDir); err != nil {
		return err
	}
	return nil
}

// MakeTarSumContext returns a build Context from a tar stream.
//
// It extracts the tar stream to a temporary folder that is deleted as soon as
// the Context is closed.
// As the extraction happens, a tarsum is calculated for every file, and the set of
// all those sums then becomes the source of truth for all operations on this Context.
//
// Closing tarStream has to be done by the caller.
func MakeTarSumContext(tarStream io.Reader) (ModifiableContext, error) {
	root, err := ioutils.TempDir("", "docker-builder")
	if err != nil {
		return nil, err
	}

	tsc := &tarSumContext{root: root}

	// Make sure we clean-up upon error.  In the happy case the caller
	// is expected to manage the clean-up
	defer func() {
		if err != nil {
			tsc.Close()
		}
	}()

	decompressedStream, err := archive.DecompressStream(tarStream)
	if err != nil {
		return nil, err
	}

	sum, err := tarsum.NewTarSum(decompressedStream, true, tarsum.Version1)
	if err != nil {
		return nil, err
	}

	if err := chrootarchive.Untar(sum, root, nil); err != nil {
		return nil, err
	}

	tsc.sums = sum.GetSums()

	return tsc, nil
}

func (b *Builder) download(srcURL string) (fi builder.FileInfo, err error) {
	// get filename from URL
	u, err := url.Parse(srcURL)
	if err != nil {
		return
	}
	path := filepath.FromSlash(u.Path) // Ensure in platform semantics
	if strings.HasSuffix(path, string(os.PathSeparator)) {
		path = path[:len(path)-1]
	}
	parts := strings.Split(path, string(os.PathSeparator))
	filename := parts[len(parts)-1]
	if filename == "" {
		err = fmt.Errorf("cannot determine filename from url: %s", u)
		return
	}

	// Initiate the download
	resp, err := httputils.Download(srcURL)
	if err != nil {
		return
	}

	// Prepare file in a tmp dir
	tmpDir, err := ioutils.TempDir("", "docker-remote")
	if err != nil {
		return
	}
	defer func() {
		if err != nil {
			os.RemoveAll(tmpDir)
		}
	}()
	tmpFileName := filepath.Join(tmpDir, filename)
	tmpFile, err := os.OpenFile(tmpFileName, os.O_RDWR|os.O_CREATE|os.O_EXCL, 0600)
	if err != nil {
		return
	}

	stdoutFormatter := b.Stdout.(*streamformatter.StdoutFormatter)
	progressOutput := stdoutFormatter.StreamFormatter.NewProgressOutput(stdoutFormatter.Writer, true)
	progressReader := progress.NewProgressReader(resp.Body, progressOutput, resp.ContentLength, "", "Downloading")
	// Download and dump result to tmp file
	if _, err = io.Copy(tmpFile, progressReader); err != nil {
		tmpFile.Close()
		return
	}
	fmt.Fprintln(b.Stdout)
	// ignoring error because the file was already opened successfully
	tmpFileSt, err := tmpFile.Stat()
	if err != nil {
		return
	}
	tmpFile.Close()

	// Set the mtime to the Last-Modified header value if present
	// Otherwise just remove atime and mtime
	mTime := time.Time{}

	lastMod := resp.Header.Get("Last-Modified")
	if lastMod != "" {
		// If we can't parse it then just let it default to 'zero'
		// otherwise use the parsed time value
		if parsedMTime, err := http.ParseTime(lastMod); err == nil {
			mTime = parsedMTime
		}
	}

	if err = system.Chtimes(tmpFileName, mTime, mTime); err != nil {
		return
	}

	// Calc the checksum, even if we're using the cache
	r, err := archive.Tar(tmpFileName, archive.Uncompressed)
	if err != nil {
		return
	}
	tarSum, err := tarsum.NewTarSum(r, true, tarsum.Version1)
	if err != nil {
		return
	}
	if _, err = io.Copy(ioutil.Discard, tarSum); err != nil {
		return
	}
	hash := tarSum.Sum(nil)
	r.Close()
	return &builder.HashedFileInfo{FileInfo: builder.PathFileInfo{FileInfo: tmpFileSt, FilePath: tmpFileName}, FileHash: hash}, nil
}