Merged in feature/from-pantheon (pull request #16)

code from pantheon

* code from pantheon

wp/wp-content/plugins/woocommerce/packages/woocommerce-blocks/src/Templates/CheckoutTemplate.php

@@ -0,0 +1,63 @@
+<?php
+namespace Automattic\WooCommerce\Blocks\Templates;
+
+use Automattic\WooCommerce\Blocks\Utils\BlockTemplateMigrationUtils;
+
+/**
+ * CheckoutTemplate class.
+ *
+ * @internal
+ */
+class CheckoutTemplate extends AbstractPageTemplate {
+	/**
+	 * Template slug.
+	 *
+	 * @return string
+	 */
+	public static function get_slug() {
+		return 'page-checkout';
+	}
+
+	/**
+	 * Returns the page object assigned to this template/page.
+	 *
+	 * @return \WP_Post|null Post object or null.
+	 */
+	protected function get_placeholder_page() {
+		$page_id = wc_get_page_id( 'checkout' );
+		return $page_id ? get_post( $page_id ) : null;
+	}
+
+	/**
+	 * True when viewing the checkout page or checkout endpoint.
+	 *
+	 * @return boolean
+	 */
+	protected function is_active_template() {
+
+		if ( ! BlockTemplateMigrationUtils::has_migrated_page( 'checkout' ) ) {
+			return false;
+		}
+
+		global $post;
+		$placeholder = $this->get_placeholder_page();
+		return null !== $placeholder && $post instanceof \WP_Post && $placeholder->post_name === $post->post_name;
+	}
+
+	/**
+	 * When the page should be displaying the template, add it to the hierarchy.
+	 *
+	 * This places the template name e.g. `cart`, at the beginning of the template hierarchy array. The hook priority
+	 * is 1 to ensure it runs first; other consumers e.g. extensions, could therefore inject their own template instead
+	 * of this one when using the default priority of 10.
+	 *
+	 * @param array $templates Templates that match the pages_template_hierarchy.
+	 */
+	public function page_template_hierarchy( $templates ) {
+		if ( $this->is_active_template() ) {
+			array_unshift( $templates, $this->get_slug() );
+			array_unshift( $templates, 'checkout' );
+		}
+		return $templates;
+	}
+}