# Contributing to OpenSubdiv

- Contributor License Agreement
- Understand Git
- Recommended Git Workflow
- Sending a Pull Request

### Contributor License Agreement

In order for us to accept code submissions (merge git pull-requests), contributors need to sign the Contributor License Agreement (CLA). There are two CLAs, one for individuals and one for corporations. As for the end-user license, both are based on Apache. They are found in the code repository (individual form, corporate form). Please email the signed CLA to opensubdiv-cla@pixar.com.

### Understand Git

First, you should familiarize yourself with the Git data model and commands.

For small changes you may not need to understand Git deeply, but for larger changes or working with the codebase over a long period of time, it becomes critical to understand more of what's going on under the hood.

There are many free resources on the internet, one which we've found useful is the following e-book:

https://github.com/pluralsight/git-internals-pdf/releases

### Recommended Git Workflow

Once you have a local development tree cloned and working, you can start making changes. You will need to integrate changes from the source tree as you work; the following outlines the workflow used by core OpenSubdiv engineers at Pixar and DreamWorks:

1. Fork the master repository into your own local copy. This can be done via the GitHub website using the "fork" button.

2. Clone your fork locally:

   > git clone <your_fork_url> OpenSubdiv.<your_name>
   > e.g.:
   > git clone https://github.com/yourusername/OpenSubdiv.git OpenSubdiv.yourusername

3. Setup two remotes, origin and upstream. Origin will be setup as a result of cloning your remote repository, but upstream must be setup manually:

   > git remote add upstream https://github.com/PixarAnimationStudios/OpenSubdiv.git

   Verify your remotes are setup correctly:

   > git remote -v

   Which should look something like:

   > origin https://github.com/yourusername/OpenSubdiv.git (fetch)
   > origin https://github.com/yourusername/OpenSubdiv.git (push)
   > upstream https://github.com/PixarAnimationStudios/OpenSubdiv.git (fetch)
   > upstream https://github.com/PixarAnimationStudios/OpenSubdiv.git (push)

   Finally, fetch the upstream content (this is required for the next step):

   > git fetch upstream

4. Setup a new branch for each change. Working with branches in Git is its greatest pleasure, we strongly suggest setting up a new branch for each change which you plan to pull-request.

   All work is done in the "dev" branch, so be sure to keep your change in sync with this upstream branch. To begin, start your new branch from the dev branch:

   > git checkout -b dev-feature upstream/dev

5. As you are working on your feature, new changes will be merged into the upstream repository, to sync these changes down and preserve your local edits, you can continually rebase your local work:

   > git pull --rebase upstream dev

   Notice the "--rebase" option here. It updates the current branch to the upstream/dev branch and rebases all edits so they are at the head of your local feature branch.

   Alternatively, you can rebase all your work at once when your feature is complete.

### Sending a Pull Request

First, rebase and squash your changes appropriately to produce a clean set of changes at the head of your tree. We require changes to be grouped locally to ensure that rolling back changes can be done easily.

If you've followed the steps above, your pending change should already be queued up as required. If you have not, you may need to rebase and squash changes at this point.

Once the change is clean, push your changes to "origin" and go to the GitHub website to submit your pull request.

Be sure to submit your request against the "dev" branch.

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