Zone diffs only include the most recent diff since tagging the repository

[nkinkade]

This may not be the right place for this issue, and could possibly be a better fit in m-lab/mlabops for the deploy_zones.yaml Ansible playbook. But I'm putting it here for now. The zone diff that site info produces and publishes only contains the diff since the repository was last tagged. If the repository was tagged multiple times since the last time the measurement-lab.org zone was deployed, then the diff will not reflect the actual difference between the published zone file and the currently generated zone file, but only the most recent changes.

This leads me to believe that the diff is not all that useful, unless we somehow make a commitment to always deploy the DNS zones after every tagging of the siteinfo repository. Otherwise, a better approach might be to have the Ansible playbook diff the currently published zone with the most recent copy in published by siteinfo.