Use ssh-agent in deploy script

deploy/deploy.sh

@@ -3,10 +3,9 @@
 set -o errexit
 set -euvo pipefail
 
-# Store ssh key in file.
-touch /tmp/key
-chmod 0600 /tmp/key
-printf "%s" "$SSH_KEY" > /tmp/key
+eval $(ssh-agent -s)
+# Register ssh key with ssh-agent.
+ssh-add - <<<"$SSH_KEY"
 
 # Add server's ssh host key to known hosts.
 mkdir -p ~/.ssh
@@ -14,8 +13,7 @@ mkdir -p ~/.ssh
 
 sshHost="${FTP_USER}@${FTP_HOST}"
 targetDir='${HOME}'"${DOMAIN_NAME}/${SUBDOMAIN}${SUBFOLDER}"
-
 rsyncTarget="${sshHost}:${targetDir}"
 
 # Upload site.
-rsync -e 'ssh -i /tmp/key' -HAXa -vi --delete ${BUILD_FOLDER}/ "${rsyncTarget}"
+rsync -HAXa -vi --delete ${BUILD_FOLDER}/ "${rsyncTarget}"