tml_filter_site_url()

function tml_filter_site_url( $url, $path, $scheme ) {
    global $pagenow;

    // Bail if currently visiting wp-login.php
    if ( 'wp-login.php' === $pagenow ) {
        return $url;
    }

    // Bail if currently customizing
    if ( is_customize_preview() ) {
        return $url;
    }

    // Parse the URL
    $parsed_url = wp_parse_url( $url );

    // Determine the path
    $path = '';
    if ( ! empty( $parsed_url['path'] ) ) {
        $path = basename( trim( $parsed_url['path'], '/' ) );
    }

    // Parse the query
    $query = array();
    if ( ! empty( $parsed_url['query'] ) ) {
        parse_str( $parsed_url['query'], $query );

        // Encode the query args
        $query = tml_array_map_recursive( 'rawurlencode', $query );
    }

    /**
     * Bail if the URL is an interim-login URL
     *
     * @see https://core.trac.wordpress.org/ticket/31821
     */
    if ( isset( $query['interim-login'] ) ) {
        return $url;
    }

    // Determine the action
    switch ( $path ) {
        case 'wp-login.php':
            // Determine the action
            $action = isset( $query['action'] ) ? $query['action'] : 'login';

            // Fix some alias actions
            if ( 'retrievepassword' === $action ) {
                $action = 'lostpassword';
            } elseif ( 'rp' === $action ) {
                $action = 'resetpass';
            }

            // Unset the action
            unset( $query['action'] );
            break;

        case 'wp-signup.php':
            $action = 'signup';
            break;

        case 'wp-activate.php':
            $action = 'activate';
            break;

        default:
            return $url;
    }

    // Bail if not a TML action
    if ( ! tml_action_exists( $action ) ) {
        return $url;
    }

    // Get the URL
    $is_network = ( 'network_site_url' === current_filter() );
    $url        = tml_get_action_url( $action, $scheme, $is_network );

    // Add the query
    $url = add_query_arg( $query, $url );

    return $url;
}

View src/includes/functions.php, line 414 on GitHub