Add the file and lint

lib/compat/wordpress-6.6/class-gutenberg-rest-edit-site-export-controller-6-6.php

@@ -0,0 +1,46 @@
+<?php
+/**
+* REST API: WP_REST_Edit_Site_Export_Controller class
+*
+* @package    WordPress
+* @subpackage REST_API
+*/
+
+/**
+* Controller which provides REST endpoint for exporting current templates
+* and template parts.
+*
+* @since 5.9.0
+*
+* @see WP_REST_Controller
+*/
+
+class WP_REST_Edit_Site_Export_Controller_6_6 extends WP_REST_Edit_Site_Export_Controller {
+	/**
+	 * Output a ZIP file with an export of the current templates
+	 * and template parts from the site editor, and close the connection.
+	 *
+	 * @since 5.9.0
+	 *
+	 * @return WP_Error|void
+	 */
+	public function export() {
+		// Generate the export file.
+		$filename = gutenberg_generate_block_templates_export_file();
+
+		if ( is_wp_error( $filename ) ) {
+			$filename->add_data( array( 'status' => 500 ) );
+
+			return $filename;
+		}
+
+		$theme_name = basename( get_stylesheet() );
+		header( 'Content-Type: application/zip' );
+		header( 'Content-Disposition: attachment; filename=' . $theme_name . '.zip' );
+		header( 'Content-Length: ' . filesize( $filename ) );
+		flush();
+		readfile( $filename );
+		unlink( $filename );
+		exit;
+	}
+}

lib/compat/wordpress-6.6/rest-api.php

@@ -78,7 +78,7 @@ function gutenberg_add_class_list_to_public_post_types() {
 add_action( 'rest_api_init', 'gutenberg_add_class_list_to_public_post_types' );
 
 /**
- * Registers the Global Styles Revisions REST API routes.
+ * Registers the Edit Site Export REST API routes.
  */
 function gutenberg_register_edit_site_export_controller_endpoints() {
     $edit_site_export_controller = new WP_REST_Edit_Site_Export_Controller_6_6();

lib/load.php

@@ -46,8 +46,8 @@ function gutenberg_is_experiment_enabled( $name ) {
 	require_once __DIR__ . '/compat/wordpress-6.5/class-gutenberg-rest-global-styles-revisions-controller-6-5.php';
 	require_once __DIR__ . '/compat/wordpress-6.5/rest-api.php';
 
-    // WordPress 6.6 compat.
-    require_once __DIR__ . '/compat/wordpress-6.6/class-gutenberg-rest-edit-site-export-controller-6-6.php';
+	// WordPress 6.6 compat.
+	require_once __DIR__ . '/compat/wordpress-6.6/class-gutenberg-rest-edit-site-export-controller-6-6.php';
 
 	// Plugin specific code.
 	require_once __DIR__ . '/class-wp-rest-global-styles-controller-gutenberg.php';