silverstripe-docsviewer/code/DocumentationManifestFileFinder.php

<?php

class DocumentationManifestFileFinder extends SS_FileFinder
{
    /**
     * @var array
     */
    private static $ignored_files = array(
        '.', '..', '.ds_store',
        '.svn', '.git', 'assets', 'themes', '_images'
    );

    /**
     * @var array
     */
    protected static $default_options = array(
        'name_regex'           => '/\.(md|markdown)$/i',
        'file_callback'        => null,
        'dir_callback'         => null,
        'ignore_vcs'           => true
    );

    /**
     * 
     */
    public function acceptDir($basename, $pathname, $depth)
    {
        $ignored =  Config::inst()->get('DocumentationManifestFileFinder', 'ignored_files');

        if ($ignored) {
            if (in_array(strtolower($basename), $ignored)) {
                return false;
            }
        }

        return true;
    }
}