file1.php

/* Override Gravity Forms activate.php template */
add_filter( 'template_include', 'activation_page' );
function activation_page( $template ) {
	$is_activation_page = isset( $_GET['page'] ) && $_GET['page'] == 'gf_activation';
	if ( !$is_activation_page ) {
		return $template;
	}
	$template_path = locate_template('activate.php');
	if ( empty($template_path) ) {
		return $template;
	}
	$template = $template_path;
	return $template;
}