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 insert(self, path, matchrecursive=True, globpats=None, repats=None):
        """Insert a directory path to this tree.

        If matchrecursive is True, mark the directory as unconditionally
        include files and subdirs recursively.

        If globpats or repats are specified, append them to the patterns being
        applied at this directory. The tricky part is those patterns can match
        "x/y/z" and visit("x"), visit("x/y") need to return True, while we
        still want visit("x/a") to return False.
        """
        if path == "":
            self.matchrecursive |= matchrecursive
            if globpats:
                # Need to match parent directories too.
                for pat in globpats:
                    components = _globpatsplit(pat)
                    parentpat = ""
                    for comp in components:
                        if parentpat:
                            parentpat += "/"
                        parentpat += comp
                        if "/" in comp:
                            # Giving up - fallback to slow paths.
                            self.unsurerecursive = True
                        self._globdirpats.append(parentpat)
                if any("**" in p for p in globpats):
                    # Giving up - "**" matches paths including "/"
                    self.unsurerecursive = True
                self._kindpats += [("glob", pat, "") for pat in globpats]
            if repats:
                if not all(map(_testrefastpath, repats)):
                    # Giving up - fallback to slow paths.
                    self.unsurerecursive = True
                self._kindpats += [("re", pat, "") for pat in repats]
            return

        subdir, rest = self._split(path)
        self.setdefault(subdir, _tree()).insert(rest, matchrecursive, globpats, repats)