As M2 sometimes developed by other people, a contribution guide is a must.
The following areas are to be covered:
- VS setup, version, tooling
- SharePoint setup
- Solution structure, codebase structure
- What can be done, how to close a ticket
- Running integration tests
- Pushing changes
Octokit's project guide is a nice one, can be used as a started to get M2 covered:
https://github.com/octokit/octokit.net/blob/master/CONTRIBUTING.md
Moved from SubPointSolutions/spmeta2#785