Document a helper script to SSH into a beaker docker container

moduleroot/.github/CONTRIBUTING.md

@@ -98,3 +98,17 @@ If you don't want to have to recreate the virtual machine every time you
 can use `BEAKER_DESTROY=no` and `BEAKER_PROVISION=no`. On the first run you will
 at least need `BEAKER_PROVISION` set to yes (the default). The Vagrantfile
 for the created virtual machines will be in `.vagrant/beaker_vagrant_fies`.
+
+When using docker you can log in using SSH. The password is always `root`. A
+simple script can be used to easily log in:
+
+```sh
+#!/bin/sh
+if [ -z $1 ] ; then
+    container=$(docker ps --quiet)
+else
+    container=$1
+fi
+ip=$(docker inspect $container | jq '.[0]["NetworkSettings"]["IPAddress"]' -r)
+ssh -o StrictHostKeyChecking=no -o UserKnownHostsFile=/dev/null root@$ip
+```