Copy parent theme's mods to child theme on activation

gistfile1.php

<?php

add_action( 'after_switch_theme', 'gowp_copy_theme_mods' );
function gowp_copy_theme_mods() {
	$mods = get_theme_mods();
	if ( is_null( $mods ) || ( ( 1 == count( $mods ) ) && ! $mods[0] ) ) {
		$parent = wp_get_theme()->get('Template');
		$child = basename( dirname( __FILE__ ) );
		update_option( "theme_mods_$child", get_option( "theme_mods_$parent" ) );
	}
}