[RFC] Change rules around automatic deploys, and add a CHANGELOG

Proposal:

This proposes 2 changes:

• Move Reaction to deploy on every PR
• Enforce adding a user-facing CHANGELOG entry for Major and Minor changes

What the RFC aims to do is:

Deployment

1. Someone makes a PR to Reaction
2. They add one of the following labels: "Deploy: Patch", "Deploy: Feature" or "Deploy: Breaking".
3. If they don’t add a label, Peril will add "Deploy: Patch" for you (basically making it the default)
4. When the PR is merged, the CI on master uses the GitHub API to determine which label is added and to deploy a version with that semantic version bump

CHANGELOG

A Danger rule can be added so that any PRs which are “Deploy: Feature” or “Deploy: Breaking” should include a user-facing changelog entry.

Reasoning

There are now 3 clients for Reaction. We want to increase visibility into what is changing, how and why. A list of PR titles are not useful enough to provide that kind of context in comparison to seeing what how useful the Emission changelog is for consumers and answering questions from product folk.

Exceptions:

There’s a possibility that you could merge a PR without one of those labels, ideally that wouldn’t happen but in that case I guess it would just not do a deploy.

Additional Context:

You can see our discussion in slack here and here

[zephraph]

@orta What about Release: Feature? It prefixes the labels with a common string (making them show up beside each other in the sort order) and explicitly states that it’ll cause a version change. I think it’d be enough to infer from that that a release would be triggered.

[orta]

This is now in production 🎉