Add details on how we use Git and GitHub to CONTRIBUTING.md.

CONTRIBUTING.md

@@ -12,6 +12,10 @@ A high level overview of our contributing guidelines.
   - [Voicing the importance of an issue](#voicing-the-importance-of-an-issue)
   - ["My issue isn't getting enough attention"](#my-issue-isnt-getting-enough-attention)
   - ["I want to help!"](#i-want-to-help)
+- [How We Use Git and GitHub](#how-we-use-git-and-github)
+  - [Branching](#branching)
+  - [Commits and Merging](#commits-and-merging)
+  - [What Goes Into a Pull Request](#what-goes-into-a-pull-request)
 - [Contributing Code](#contributing-code)
   - [Setting Up Your Development Environment](#setting-up-your-development-environment)
     - [Customizing `config/kibana.dev.yml`](#customizing-configkibanadevyml)
@@ -65,6 +69,31 @@ Feel free to bump your issues if you think they've been neglected for a prolonge
 
 We enjoy working with contributors to get their code accepted. There are many approaches to fixing a problem and it is important to find the best approach before writing too much code.
 
+## How We Use Git and GitHub
+
+### Branching
+
+* All work on the next major release goes into master.
+* Past major release branches are named `{majorVersion}.x`. They contain work that will go into the next minor release.
+* Past minor release branches are named `{majorVersion}.{minorVersion}`. They contain work that will go into the next patch release.
+* All work is done on feature branches and merged into one of these branches.
+* Where appropriate, we'll backport changes into older release branche.
+
+### Commits and Merging
+
+* Feel free to make as many commits as you want, while working on a branch.
+* When submitting a PR for review, please perform an interactive rebase to present a logical history that's easy for the reviewers to follow.
+* Please use your commit messages to include helpful information on your changes, e.g. changes to APIs, UX changes, bugs fixed, and an explanation of *why* you made the changes that you did.
+* Resolve merge conflicts by rebasing the target branch over your feature branch, and force-pushing.
+* When merging, we'll squash your commits into a single commit.
+
+### What Goes Into a Pull Request
+
+* Please include an explanation of your changes in your PR description.
+* Links to relevant issues, external resources, or related PRs are very important and useful.
+* Please update any tests that pertain to your code, and add new tests where appropriate.
+* See [Submitting a Pull Request](#submitting-a-pull-request) for more info.
+
 ## Contributing Code
 
 These guidelines will help you get your Pull Request into shape so that a code review can start as soon as possible.