Dockerfile: add a dockerfile that install docurium with its dependencies

[carlosmn]

You can supposedly make this repo into an action like this so let's see how that goes.

Right now you run things like

docker build . -t docurium
docker run -v $SRC:/workspace -it docurium
# cd /workspace && cm doc api.docurium

It currently fails to create the actual commit because it really wants you to have configured your identity in git but this should work as a first step to play around with it.

[carlosmn]

I've updated the Dockerfile to try to avoid it blowing up in size by using a multistage build and copying over the relevant files into a leaner image.

This still blows up if you don't take extra care to mount your git configuration. I'm not sure what the right thing to do here is to make it easier to user the container. We could mount the different places your user-level configuration might be, or maybe we should accept an environment variable that docurium should use if they exist?

[tiennou]

Can you clarify what are you planning to use that Docker build for ? I thought it was about having a demo sandbox, then I wanted some developer one, and now that Dockerfile looks like it should "just work™", but with Linux-specific paths…

[carlosmn]

I don't know what you mean with Linux-specific paths. This Dockerfile builds a Debian image so any paths are what works there.

My idea for this image is that you can use it to generate documentation either locally or as a CI step or an Action or whatever, without having to figure out what the dependencies are for it or which version of llvm happens to work now.

[tiennou]

I missed that builder is an alias for the debian-stretch image, thus got confused by /var/lib. Sorry about that.

I'll have to investigate Actions then, that sounds crazy good. Thus I'm fine to if you are, because I've used it already to check how non-macOS reacts.

[carlosmn]

I still need to figure out what to do about the signature for the commit it crates, but otherwise I'm pretty happy with it. The multi-stage build can be a bit confusing (it's taken me two days to get to this comparatively simple set of rules) but it does mean that we have a ~475MB image instead of the ~1.5GB monstrosity that comes out if you leave everything installed.