def download_file(url, dest=None, chunk_size=1024, replace="ask",
                  label="Downloading {dest_basename} ({size:.2f}MB)",
                  expected_extension=None):
    """Download a file from a given URL and display progress.

    :param dest: If the destination exists and is a directory, the filename
        will be guessed from the Content-Disposition header. If the destination
        is an existing file, the user will either be prompted to overwrite, or
        the file will be replaced (depending on the value of **replace**). If
        the destination does not exist, it will be used as the filename.
    :param int chunk_size: bytes read in at a time.
    :param replace: If `False`, an existing destination file will not be
        overwritten.
    :param label: a string which is formatted and displayed as the progress bar
        label. Variables provided include *dest_basename*, *dest*, and *size*.
    :param expected_extension: if set, the filename will be sanitized to ensure
        it has the given extension. The extension should not start with a dot
        (`.`).
    """
    dest = Path(dest or url.split("/")[-1])
    response = get(url, stream=True)
    if (dest.exists()
            and dest.is_dir()
            and "Content-Disposition" in response.headers):
        content_disposition = rfc6266.parse_requests_response(response)
        if expected_extension is not None:
            filename = content_disposition.filename_sanitized(
                expected_extension)
        filename = secure_filename(filename)
        dest = dest / filename
    if dest.exists() and not dest.is_dir():
        if (replace is False
                or replace == "ask"
                and not click.confirm("Replace {}?".format(dest))):
            return str(dest)
    size = int(response.headers.get("content-length", 0))
    label = label.format(dest=dest, dest_basename=dest.name,
                         size=size/1024.0/1024)
    with click.open_file(str(dest), "wb") as f:
        content_iter = response.iter_content(chunk_size=chunk_size)
        with click.progressbar(content_iter, length=size/1024,
                               label=label) as bar:
            for chunk in bar:
                if chunk:
                    f.write(chunk)
                    f.flush()
    return str(dest)
def fetch_new(self, dest, url, rev_options):
        # type: (str, HiddenText, RevOptions) -> None
        rev_display = rev_options.to_display()
        logger.info('Cloning %s%s to %s', url, rev_display, display_path(dest))
        self.run_command(make_command('clone', '-q', url, dest))

        if rev_options.rev:
            # Then a specific revision was requested.
            rev_options = self.resolve_revision(dest, url, rev_options)
            branch_name = getattr(rev_options, 'branch_name', None)
            if branch_name is None:
                # Only do a checkout if the current commit id doesn't match
                # the requested revision.
                if not self.is_commit_id_equal(dest, rev_options.rev):
                    cmd_args = make_command(
                        'checkout', '-q', rev_options.to_args(),
                    )
                    self.run_command(cmd_args, cwd=dest)
            elif self.get_current_branch(dest) != branch_name:
                # Then a specific branch was requested, and that branch
                # is not yet checked out.
                track_branch = 'origin/{}'.format(branch_name)
                cmd_args = [
                    'checkout', '-b', branch_name, '--track', track_branch,
                ]
                self.run_command(cmd_args, cwd=dest)

        #: repo may contain submodules
        self.update_submodules(dest)