Drupal 8.0.0 beta 12. More info: https://www.drupal.org/node/2514176

sites/example.settings.local.php

@@ -0,0 +1,57 @@
+<?php
+
+/**
+ * @file
+ * Local development override configuration feature.
+ *
+ * To activate this feature, copy and rename it such that its path plus
+ * filename is 'sites/example.com/settings.local.php', where example.com
+ * is the name of your site. Then, go to the bottom of
+ * 'sites/example.com/settings.php' and uncomment the commented lines that
+ * mention 'settings.local.php'.
+ */
+
+/**
+ * Enable local development services.
+ */
+$settings['container_yamls'][] = DRUPAL_ROOT . '/sites/development.services.yml';
+
+/**
+ * Show all error messages, with backtrace information.
+ */
+$config['system.logging']['error_level'] = 'verbose';
+
+/**
+ * Disable CSS and JS aggregation.
+ */
+$config['system.performance']['css']['preprocess'] = FALSE;
+$config['system.performance']['js']['preprocess'] = FALSE;
+
+/**
+ * Disable the render cache (this includes the page cache).
+ *
+ * This setting disables the render cache by using the Null cache back-end
+ * defined by the development.services.yml file above.
+ *
+ * Do not use this setting until after the site is installed.
+ */
+$settings['cache']['bins']['render'] = 'cache.backend.null';
+
+/**
+ * Allow test modules and themes to be installed.
+ *
+ * Drupal ignores test modules and themes by default for performance reasons.
+ * During development it can be useful to install test extensions for debugging
+ * purposes.
+ */
+$settings['extension_discovery_scan_tests'] = TRUE;
+
+/**
+ * Enable access to rebuild.php.
+ *
+ * This setting can be enabled to allow Drupal's php and database cached
+ * storage to be cleared via the rebuild.php page. Access to this page can also
+ * be gained by generating a query string from rebuild_token_calculator.sh and
+ * using these parameters in a request to rebuild.php.
+ */
+$settings['rebuild_access'] = TRUE;