src/Composer/Util/RemoteFilesystem.php
private function isPublicBitBucketDownload($urlToBitBucketFile)
    {
        $domain = parse_url($urlToBitBucketFile, PHP_URL_HOST);
        if (strpos($domain, 'bitbucket.org') === false) {
            // Bitbucket downloads are hosted on amazonaws.
            // We do not need to authenticate there at all
            return true;
        }

        $path = parse_url($urlToBitBucketFile, PHP_URL_PATH);

        // Path for a public download follows this pattern /{user}/{repo}/downloads/{whatever}
        // {@link https://blog.bitbucket.org/2009/04/12/new-feature-downloads/}
        $pathParts = explode('/', $path);

        return count($pathParts) >= 4 && $pathParts[3] == 'downloads';
    }
private function isPublicBitBucketDownload($urlToBitBucketFile)
    {
        $domain = parse_url($urlToBitBucketFile, PHP_URL_HOST);
        if (strpos($domain, 'bitbucket.org') === false) {
            // Bitbucket downloads are hosted on amazonaws.
            // We do not need to authenticate there at all
            return true;
        }

        $path = parse_url($urlToBitBucketFile, PHP_URL_PATH);

        // Path for a public download follows this pattern /{user}/{repo}/downloads/{whatever}
        // {@link https://blog.bitbucket.org/2009/04/12/new-feature-downloads/}
        $pathParts = explode('/', $path);

        return count($pathParts) >= 4 && $pathParts[3] == 'downloads';
    }
@link https://github.com/composer/composer/issues/5584

@param string $urlToBitBucketFile URL to a file at bitbucket.org.

@return bool Whether the given URL is a public BitBucket download which requires no authentication.