More seamless integration with Infracost

[alikhajeh1]

Hi everyone, I've been helping many Atlantis users setup Infracost and one common challenge I see is for users to pick between:

1. using the official Atlantis Docker image and adding a custom run step to curl the $PLANFILE to the Infracost Plan JSON API. This is not great due to potential security issues. We'd like to open source that API as part of the Cloud Pricing API but that requires the user to run another server.
2. rolling your own image, again not great as you have to push it somewhere and keep it uptodate.
3. using the infracost-atlantis image, which most users pick.

We don't mind keeping the infracost-atlantis image up to date but I noticed that conftest was added to the Atlantis image a few months ago, and wondered if the community wants to have infracost (+ compost) be included in the official Atlantis image?

That plus #1954 seems like a 90 / 10 solution: gets 90% of what Atlantis-Infracost users want with only 10 of the work.

One other option might be native integration, I suppose similar to conftest, but that seems to require much more effort.

[alikhajeh1]

We just released a big improvement to the Infracost-Atlantis integration 🎉 As part of that we now maintain pre-built Docker images that extend the official Atlantis image and include Infracost. We maintain tags for the latest two 0.x versions of Atlantis:

• infracost/infracost-atlantis:atlantis0.18-infracost0.9 latest patch version of Atlantis v0.18 and Infracost v0.9
• infracost/infracost-atlantis:atlantis0.17-infracost0.9 latest patch version of Atlantis v0.17 and Infracost v0.9
• infracost/infracost-atlantis:latest latest versions of Atlantis and Infracost

If you already use a custom Docker image for Atlantis, copy the top RUN command from this Dockerfile into your Dockerfile.

We've written a migration guide - if you have any issues please join the Atlantis Slack channel (or the Infracost community chat) and we'd be happy to help quickly 😄