WordPress at a glance
function is not described

wp_restore_post_revision() WP 2.6.0

Restores a post to the specified revision.

Can restore a past revision using all fields of the post revision, or only selected fields.

Hooks in function
Return

Int/false/null. Null if error, false if no fields to restore, (int) post ID if success.

Usage

wp_restore_post_revision( $revision_id, $fields );
$revision_id(int/WP_Post) (required)
Revision ID or revision object.
$fields(array)
What fields to restore from.
Default: all

Code of wp restore post revision: wp-includes/revision.php VER 5.0.3

<?php
function wp_restore_post_revision( $revision_id, $fields = null ) {
	if ( !$revision = wp_get_post_revision( $revision_id, ARRAY_A ) )
		return $revision;

	if ( !is_array( $fields ) )
		$fields = array_keys( _wp_post_revision_fields( $revision ) );

	$update = array();
	foreach ( array_intersect( array_keys( $revision ), $fields ) as $field ) {
		$update[$field] = $revision[$field];
	}

	if ( !$update )
		return false;

	$update['ID'] = $revision['post_parent'];

	$update = wp_slash( $update ); //since data is from db

	$post_id = wp_update_post( $update );
	if ( ! $post_id || is_wp_error( $post_id ) )
		return $post_id;

	// Update last edit user
	update_post_meta( $post_id, '_edit_last', get_current_user_id() );

	/**
	 * Fires after a post revision has been restored.
	 *
	 * @since 2.6.0
	 *
	 * @param int $post_id     Post ID.
	 * @param int $revision_id Post revision ID.
	 */
	do_action( 'wp_restore_post_revision', $post_id, $revision['ID'] );

	return $post_id;
}