Sets the current WP_Query to return auto-draft posts.

The auto-draft status indicates a new post, so allow the the WP_Query instance to
return an auto-draft post for template resolution when editing a new post.

function _resolve_template_for_new_post( $wp_query ) {
	if ( ! $wp_query->is_main_query() ) {
		return;
	}

	remove_filter( 'pre_get_posts', '_resolve_template_for_new_post' );

	// Pages.
	$page_id = isset( $wp_query->query['page_id'] ) ? $wp_query->query['page_id'] : null;

	// Posts, including custom post types.
	$p = isset( $wp_query->query['p'] ) ? $wp_query->query['p'] : null;

	$post_id = $page_id ? $page_id : $p;
	$post    = get_post( $post_id );

	if (
		$post &&
		'auto-draft' === $post->post_status &&
		current_user_can( 'edit_post', $post->ID )
	) {
		$wp_query->set( 'post_status', 'auto-draft' );
	}
}