Contributing to Cobalt

We‘d love to hear about how you would like to contribute to Cobalt! It’s worth reading through this modest document first, to understand the process and to make sure you know what to expect.

Before You Contribute

As an Individual

Before Cobalt can use your code, as an unaffiliated individual, you must sign the Google Individual Contributor License Agreement (CLA), which you can do online.

As a Company

If you are a company that wishes to have one or more employees contribute to Cobalt on-the-clock, that is covered by a different agreement, the Software Grant and Corporate Contributor License Agreement.

What is a CLA?

The Contributor License Agreement is necessary mainly because you own the copyright to your changes, even after your contribution becomes part of our codebase, so we need your permission to use and distribute your code. We also need to be sure of various other things — for instance that you‘ll tell us if you know that your code infringes on other people’s patents. You don‘t have to sign the CLA until after you’ve submitted your code for review and a member has approved it, but you must do it before we can put your code into our codebase. Before you start working on a larger contribution, you should get in touch with us first with your idea so that we can help out and possibly guide you. Coordinating up front makes it much easier to avoid frustration later on.

Code Reviews

All submissions, including submissions by project members, require review. We currently use Gerrit Code Review for this purpose. Currently, team-member submissions go through private reviews, and external submissions go through public reviews.

Submission Process

We admit that this submission process is currently not completely optimized to make contributions easy, and we hope to make improvements to it in the future. It will always include some form of signing the CLA and submitting the code for review before merging changes into the Cobalt master tree.

  1. Ensure you or your company have signed the appropriate CLA (see “Before You Contribute” above).
  2. Rebase your changes down into a single git commit.
  3. Run git clang-format HEAD~ to apply default C++ formatting rules, followed by git commit -a --amend to squash any formatting changes into your commit.
  4. Run git push origin HEAD:refs/for/master to upload the review to Cobalt's Gerrit instance.
  5. Someone from the maintainers team will review the code, putting up comments on any things that need to change for submission.
  6. If you need to make changes, make them locally, test them, then git commit --amend to add them to the existing commit. Then return to step 2.
  7. If you do not need to make any more changes, a maintainer will integrate the change into our private repository, and it will get pushed out to the public repository after some time.