Document customizations that require their own Dockerfile

[choldgraf]

Description

This repository focuses on a more straightforward environment where people need a "vanilla" repo2docker setup in order to get the image running. This is super useful for most communities, though I think that there's an "advanced use-case" that we should cover as well, which is rolling your own Dockerfile.

The most obvious use-case that this enables is when you want to start with a different base image, which is not currently possible with repo2docker.

Benefit

There are many communities that want to use other images as a base, since a lot of communities maintain base images that are meant to help with reproducibility. One non-python example is the rocker project in the R community.

Implementation

As @sgibson91 noted, a good reference to use for inspiration would be the COESSING image repository, which does some more complex setup.

Another thing we should consider is that we might extend this repository to use more complex build files. For example, if people wanted an example using a postBuild script to configure the Jupyter server. I think the question boils down to "how many use-cases require the use of a Dockerfile (like using a different base image) vs. how many can we just show off more complex repo2docker setups w/o a Dockerfile.

Tasks

• Understand what other use-cases are best-suited to a Dockerfile
• Decide whether they make sense to include in this repository, vs. splitting into a separate template repository

[damianavila]

I do think we should map different levels of complexity with different repo templates.
That should be easier to consume from a user perspective, IMHO.

[sgibson91]

It becomes much easier to create a new repo for a new hub too - just click the template button.