WP_Upgrader::restore_temp_backup()

	public function restore_temp_backup() {
		global $wp_filesystem;

		$errors = new WP_Error();

		foreach ( $this->temp_restores as $args ) {
			if ( empty( $args['slug'] ) || empty( $args['src'] ) || empty( $args['dir'] ) ) {
				return false;
			}

			if ( ! $wp_filesystem->wp_content_dir() ) {
				$errors->add( 'fs_no_content_dir', $this->strings['fs_no_content_dir'] );
				return $errors;
			}

			$src      = $wp_filesystem->wp_content_dir() . 'upgrade-temp-backup/' . $args['dir'] . '/' . $args['slug'];
			$dest_dir = $wp_filesystem->find_folder( $args['src'] );
			$dest     = trailingslashit( $dest_dir ) . $args['slug'];

			if ( $wp_filesystem->is_dir( $src ) ) {
				// Cleanup.
				if ( $wp_filesystem->is_dir( $dest ) && ! $wp_filesystem->delete( $dest, true ) ) {
					$errors->add(
						'fs_temp_backup_delete',
						sprintf( $this->strings['temp_backup_restore_failed'], $args['slug'] )
					);
					continue;
				}

				// Move it.
				$result = move_dir( $src, $dest, true );
				if ( is_wp_error( $result ) ) {
					$errors->add(
						'fs_temp_backup_delete',
						sprintf( $this->strings['temp_backup_restore_failed'], $args['slug'] )
					);
					continue;
				}
			}
		}

		return $errors->has_errors() ? $errors : true;
	}