puppet: environments are sticky!

howto/puppet.md

@@ -153,6 +153,13 @@ flag. For example, this will switch a node from `production` to
 
     puppet agent --test --environment test
 
+Note that this setting is **sticky**: further runs will *keep* the
+`test` environment even if the `--environment` flag is not set, as the
+setting is written in the `puppet.conf`. To reset to the `production`
+environment, you can simply use that flag again:
+
+    puppet agent --test --environment test
+
 A node or group of nodes can be switch to a different environment
 using the [external node classifier](#external-node-classifier-enc).
 
@@ -173,6 +180,15 @@ avoid overly broad debugging statements, if any, and to generally keep an
 active eye on feature branches so as to prevent the accumulation of unreviewed
 code.
 
+Finally, note that environments are automatically destroyed (alongside
+their branch) on the Puppet server after 2 weeks since the last
+commit to the branch. An email warning about this will be sent to the
+author of that last commit. This doesn't destroy the mirrored branch
+on GitLab.
+
+When an environment is removed, Puppet agents will revert back to the
+`production` environment automatically.
+
 ### Modifying an existing configuration
 
 For new deployments, this is *NOT* the preferred method. For example,