(GH-901) Document branches for use with Sensu versions 1 and 2

CONTRIBUTING.md

@@ -16,3 +16,51 @@
 ## Commits
 
   - Squash/rebase any commits where possible to reduce the noise in the PR
+
+## Git commits
+
+Reference the issue number, in the format `(GH-###)`.
+
+```
+(GH-901) Add support for Sensu v2
+```
+
+## Versions
+
+v2 of this module supports Sensu v1
+v3 of this module supports Sensu v2
+
+## Branches
+
+### master
+
+The `master` branch is for development against Sensu v1. Once Sensu v2
+is no longer beta, master will switch to target that.
+
+### sensu2
+
+The `sensu2` branch is for development against Sensu v2. Please target
+any commits for Sensu v2 against this branch.
+
+### sensu1
+
+The `sensu1` branch does not exist yet, though will once master targets
+Sensu v2. Sensu v1 will continue to be supported and changes to that
+version would then target this branch.
+
+# Release process
+
+1. update version in `metadata.json`
+1. run `github_changelog_generator`
+1. update `CHANGELOG.md` and change `unreleased` at the top to the
+   version, such as `v2.0.0`, and change `HEAD` to the same version,
+   such as `v2.0.0`.
+1. Update `REFERENCE.md` with the command `bundle exec rake reference`
+1. Commit changes and push to master
+1. Tag the new version, such as `git tag -a 'v2.0.0' -m 'v2.0.0'`
+1. Push tags `git push --tags`
+1. Update the puppet strings documentation with `bundle exec rake strings:gh_pages:update`
+1. Clean up tests with `bundle exec rake spec_clean`
+1. Remove junit directory from beaker runs `rm -fr junit`
+1. Build module with `puppet module build`
+1. Upload module to Puppet Forge.