Prebuilt dev environments for easier onboarding and code reviews

[svenefftinge]

Hey @juliusv,

This PR adds configuration for Gitpod to this repo.
It allows anyone to quickly spin up fresh prebuilt dev environment in a browser for any branches, issues and pull requests.
I have configured it to prebuild your branches using (i.e. the init task in .gitpod.yml)

make build

On start it launches prometheus with the example config

./prometheus --config.file=documentation/examples/prometheus.yml

in one terminal and the web UI in a separate one:

cd web/ui/react-app
yarn start

I hope the config is a good start. Please propose any changes to align better with your daily routines and use cases.

To get the prebuilds, you also need to install the GitHub app on this project. Without the app the config works, but users will have to wait for the init task (make build).

You can try the experience on my fork https://gitpod.io/#https://github.com/svenefftinge/prometheus
Or even review this PR using gitpod by prefixing the URL of this page with gitpod.io#.

[roidelapluie]

Thank you for bringing this idea.

I feel like this should be discussed on our developers mailing list: https://groups.google.com/forum/#!forum/prometheus-developers rather than in a pull request.

[roidelapluie]

I will close this PR for now ; let's see what the discussions of the mailing list will give.

[juliusv]

To be fair, in a conversation with the nice people from Gitpod they mentioned their CI capabilities and I thought it sounded so awesome that I proposed them to send a PR :) But yeah, so you think we should discuss this first? It's going to add a CI check badge, and the benefit will be that you can immediately jump into an online container+IDE for any PR branch (with the binary pre-built), to further poke around at both the code and the actual behavior, without having to check out a PR branch locally. I think that's super cool :)

[juliusv]

I'll open a discussion on prometheus-developers.