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Git and Pull requests

Contributions are submitted, reviewed, and accepted using GitHub pull requests.
The latest changes are in the master branch. PR's should initially target this branch.
Try to make clean commits that are easily readable (including descriptive commit messages!)
See the test-specific README.md for instructions on running the test suite. Test before you push. Get familiar with Unish, our test suite. Optionally run tests in the provided Docker containers.
We maintain branches named 9.x, 8.x, etc. These are release branches. From these branches, we make new tags for patch and minor versions.

Development Environment

You may choose to use the docker-compose file in root directory for an optimized environment.
See composer run-script -l for a list of helper scripts.

Do write comments. You don't have to comment every line, but if you come up with something thats a bit complex/weird, just leave a comment. Bear in mind that you will probably leave the project at some point and that other people will read your code. Undocumented huge amounts of code are nearly worthless!
We use PSR-2 in the /src directory. Drupal's coding standards are still used in the includes directory (deprecated code).
Keep it compatible. Do not introduce changes to the public API, or configurations too casually. Don't make incompatible changes without good reasons!

The docs are in the docs and examples folders in the git repository, so people can easily find the suitable docs for the current git revision. You can read these from within Drush, with the drush topic command.
Documentation should be kept up-to-date. This means, whenever you add a new API method, add a new hook or change the database model, pack the relevant changes to the docs in the same pull request.