added timestamp for main branch

Jenkinsfile

@@ -12,7 +12,7 @@ pipeline {
                 [ -d ~/.ssh ] || mkdir ~/.ssh && chmod 0700 ~/.ssh
                 ssh-keyscan -t rsa,dsa baltimore-wiki.lxd >> ~/.ssh/known_hosts
                 ssh mdbook@baltimore-wiki.lxd << EOF
-                    echo "main branch" >> ~/test
+                    echo "$(date): main branch" >> ~/test
 EOF
                 '''
             }