Fix #3063. Add example of dynamic alias alter (#3115)

examples/Commands/SiteAliasAlterCommands.php

@@ -0,0 +1,41 @@
+<?php
+namespace Drush\Commands;
+
+use Consolidation\AnnotatedCommand\AnnotationData;
+use Drush\SiteAlias\SiteAliasManagerAwareInterface;
+use Drush\SiteAlias\SiteAliasManagerAwareTrait;
+use Robo\Common\ConfigAwareTrait;
+use Robo\Contract\ConfigAwareInterface;
+use Symfony\Component\Console\Input\InputInterface;
+
+/**
+ * Load this example by using the --include option - e.g. `drush --include=/path/to/drush/examples`
+ */
+class SiteAliasAlterCommands extends DrushCommands implements SiteAliasManagerAwareInterface, ConfigAwareInterface  {
+
+  use SiteAliasManagerAwareTrait;
+  use ConfigAwareTrait;
+
+  /**
+   * A few example alterations to site aliases.
+   *
+   * @hook pre-init *
+   *
+   * @param \Symfony\Component\Console\Input\InputInterface $input
+   * @param \Consolidation\AnnotatedCommand\AnnotationData $annotationData
+   */
+  public function alter(InputInterface $input, AnnotationData $annotationData) {
+    $self = $this->siteAliasManager()->getSelf();
+    if ($self->isRemote()) {
+
+      // Always pass along ssh keys.
+      if (!$self->has('ssh.options')) {
+        // Don't edit the alias - edit the general config service instead.
+        $this->getConfig()->set('ssh.options', '-o ForwardAgent=yes');
+      }
+
+      // Change the SSH user.
+      $input->setOption('remote-user', 'mw2');
+    }
+  }
+}

examples/example.aliases.yml

@@ -201,7 +201,7 @@
 #
 # Altering aliases:
 #
-# It is no longer possible to alter aliases dynamically. This is a planned feature. Help wanted.
+# See examples/Commands/SiteAliasAlter.php for an example.
 #
 # Environment variables:
 #