def recurse_tree(rootpath, excludes, opts):
    # type: (unicode, List[unicode], Any) -> List[unicode]
    """
    Look for every file in the directory tree and create the corresponding
    ReST files.
    """
    if INITPY in os.listdir(rootpath):
        path_prefix = path.sep.join(rootpath.split(path.sep)[:-1])
    else:
        path_prefix = rootpath

    toplevels = []
    followlinks = getattr(opts, 'followlinks', False)
    includeprivate = getattr(opts, 'includeprivate', False)
    implicit_namespaces = getattr(opts, 'implicit_namespaces', False)
    for root, subs, files in walk(rootpath, followlinks=followlinks):
        # document only Python module files (that aren't excluded)
        py_files = sorted(f for f in files
                          if path.splitext(f)[1] in PY_SUFFIXES and
                          not is_excluded(path.join(root, f), excludes))
        is_pkg = INITPY in py_files
        if is_pkg:
            py_files.remove(INITPY)
            py_files.insert(0, INITPY)
        elif root != rootpath:
            # only accept non-package at toplevel unless using implicit
            # namespaces
            if not implicit_namespaces:
                del subs[:]
                continue
        # remove hidden ('.') and private ('_') directories, as well as
        # excluded dirs
        if includeprivate:
            exclude_prefixes = ('.',)  # type: Tuple[unicode, ...]
        else:
            exclude_prefixes = ('.', '_')
        subs[:] = sorted(sub for sub in subs
                         if not sub.startswith(exclude_prefixes) and
                         not is_excluded(path.join(root, sub), excludes))

        pkg = root[len(path_prefix):].lstrip(path.sep).replace(path.sep, '.')
        for py_file in py_files:
            if not shall_skip(path.join(root, py_file), opts):
                if py_file == INITPY:
                    module = ''
                else:
                    module = path.splitext(py_file)[0]
                toplevels.append(makename(pkg, module))

    return toplevels
Look for every file in the directory tree and create the corresponding
    ReST files.