Add a multi-stage Dockerfile

[sylr]

This makes it easy to build a thanos image without a proper dev env set up.

Also allows to build images using quay.io or docker hub services.

[bwplotka]

Can we replace existing docker with this for clean view? (:

[sylr]

We absolutely can but each time I tried to propose this I got "we prefer to build it outside docker and package it afterward"

[bwplotka]

Ah, my bad did not look closer.

So I think this is quite useful and keeping it here seems ok as well. We have 2 options. Leave 2 Dockerfiles, but worth to name them better? For example Dockerfile (for the thing we have now) and Dockerfile_dev.multi-step for this one?

Otherwise we can do single multi stage with 3 images. 2 as you created, and 3rd with just copy without --from so what we have right now. Then we can name all 3 and run docker build with proper --target (: What do you think? From our point of view we used it with Makefile and CI only, so as long as make docker and make docker-push works, we are fine. But we would like to keep simple copy pattern, and allow full build+copy as optional thing.

[sylr]

I don't understand the purpose of a multi stage Dockerfile if the last stage does not copy the build results of the previous stages.

As for the name I'd keep it like that I don't like the _dev addition and it's really name multi-stage builds not multi-step.

[bwplotka]

Sure, let's do that (: So maybe at least make docker-multi-stage will be useful then?

[bwplotka]

I don't understand the purpose of a multi stage Dockerfile if the last stage does not copy the build results of the previous stages.

Some of them has, rest you can explicitly run using --target, but I agree it might super confusing idea I proposed (:

[sylr]

Sure, let's do that (: So maybe at least make docker-multi-stage will be useful then?

That I can do.

[bwplotka]

Thanks! Awesome.