This is awesome.

Vlad's blog post at https://vladaionescu.com/introducing-earthly-build-automatio... is a shorter introduction.

Reminds me of SourceHut's CI infrastructure (that uses VMs, rather than containers, and IIRC doesn't natively multi-stage in the same way - but has a similar use profile)

It's basically Makefile + Dockerfile combined. That's useful because you can get rid of ad-hoc shell scripts, and builds are deterministic.

The ability to create a docker image from multiple sub-images is pretty useful. I think you could also use Dockerfile multi stage builds for that, but it’s not as clean.