Update /drush dir for Drush9

Shows how the benefits of a policyfile and also illustrates where to store site aliases and druh config.

drush/Commands/PolicyCommands.php

@@ -0,0 +1,55 @@
+<?php
+namespace Drush\Commands;
+
+use Consolidation\AnnotatedCommand\CommandData;
+use Drush\Commands\DrushCommands;
+use Symfony\Component\Console\Input\InputOption;
+
+/**
+ * Edit this file to reflect your organization's needs.
+ */
+
+class PolicyCommands extends DrushCommands {
+
+  /**
+   * Prevent catastrophic braino. Note that this file has to be local to the
+   * machine that initiates the sql:sync command.
+   *
+   * hook validate sql:sync
+   *
+   * @throws \Exception
+   */
+  public function sqlSyncValidate(CommandData $commandData) {
+    if ($commandData->input()->getArgument('destination') == '@prod') {
+      throw new \Exception(dt('Per !file, you may never overwrite the production database.', ['!file' => __FILE__]));
+    }
+  }
+
+  /**
+   * Limit rsync operations to production site.
+   *
+   * hook validate core:rsync
+   */
+  public function rsyncValidate(CommandData $commandData) {
+    if (preg_match("/^@prod/", $commandData->input()->getArgument('destination'))) {
+      throw new \Exception(dt('Per !file, you may never rsync to the production site.', ['!file' => __FILE__]));
+    }
+  }
+
+  /**
+   * Unauthorized may not execute updates.
+   *
+   * @hook validate updatedb
+   */
+  public function validateUpdateDb(CommandData $commandData) {
+    if (!$commandData->input()->getOption('secret') == 'mysecret') {
+      throw new \Exception(dt('UpdateDb command requires a secret token per site policy.'));
+    }
+  }
+
+  /**
+   * @hook option updatedb
+   * @option secret A required token else user may not run updatedb command.
+   */
+  public function optionsetUpdateDb($options = ['secret' => self::REQ]) {}
+}

drush/Sites/self.site.yml

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+# Edit or remove this file as needed.
+# Docs at https://github.com/drush-ops/drush/blob/master/examples/example.site.yml
+
+#live:
+#  host: live.domain.com
+#  user: www-admin
+#  root: /path/to/drupal
+#  uri: http://www.example.com
+#
+#stage:
+#  host: stage.domain.com
+#  user: www-admin
+#  root: /path/to/drupal
+#  uri: http://stage.example.com

drush/drush.yml

@@ -0,0 +1,2 @@
+# A Drush configuration file.
+# Details at https://github.com/drush-ops/drush/blob/master/examples/example.drush.yml