[byroot]

It's better to have an activity log of your deployments, that way by querying what commit is currently in production you can compare it with the log and know what actually commit range was deployed.

There is many tools to do that, e.g.

  - Shopify's Shipit: https://github.com/shopify/shipit-engine (author here)
  - Zendesk's Samson: https://github.com/zendesk/samson
  -  Netflix's Spinnaker: http://techblog.netflix.com/2015/11/global-continuous-delivery-with.html
  - Yahoo's Screwdriver: https://yahooeng.tumblr.com/post/155765242061/open-sourcing-screwdriver-yahoos-continuous
  - Instagram's Sauron: https://engineering.instagram.com/continuous-deployment-at-instagram-1e18548f01d1#.tv6zycskx

And the list goes on.