add SSH key as in GitLab instructions

deploy.sh

-#!/bin/sh
+#!/bin/bash
 
 # Run ssh-agent and add ssh key.
 eval $(ssh-agent -s)
-ssh-add <(echo "$SSH_KEY")
+
+echo "$SSH_PRIVATE_KEY" | tr -d '\r' | ssh-add - > /dev/null
 
 # Add server's ssh host key to known hosts.
 mkdir -p ~/.ssh
-[[ -f /.dockerenv ]] && echo "$SSH_SERVER_HOSTKEYS" > ~/.ssh/known_hosts
 
-# Install rsync.
-# apt-get update
-# apt-get install -y rsync
+chmod 700 ~/.ssh
+
+[[ -f /.dockerenv ]] && echo "$SSH_SERVER_HOSTKEYS" > ~/.ssh/known_hosts
 
 # Upload site.
 rsync -r --verbose --compress --delete ./docs/_build/html/* \