## How to contribute

Yorkie is Apache 2.0 licensed and accepts contributions via GitHub pull requests
. This document outlines some conventions on commit message formatting,
contact points for developers, and other resources to help get contributions
into Yorkie.

### Contacts

If you have any questions along the way, please don’t hesitate to ask us
- Discord: [Yorkie Discord](https://discord.com/invite/MVEAwz9sBy).

### Getting started

- Fork the repository on GitHub
- Read the README.md for build instructions

## Contribution flow

This is a rough outline of what a contributor's workflow looks like:

- Create a topic branch from where to base the contribution (usually main).
- Make commits of logical units.
- Make sure commit messages are in the proper format (see below).
- Push changes in a topic branch to a personal fork of the repository.
- Make sure all tests pass, and add any new tests as appropriate.
- Submit a pull request to the original repository.
- The PR must receive a LGTM from maintainers.

Thanks for contributing!

### Code style

In order to format the code, we use [SwiftFormat](https://github.com/nicklockwood/SwiftFormat) and [SwiftLint](https://github.com/realm/SwiftLint).

### Format of the commit message

We follow a rough convention for commit messages that is designed to answer two
questions: what changed and why. The subject line should feature the what and
the body of the commit should describe the why.

```
Remove the synced seq when detaching the document

To collect garbage like CRDT tombstones left on the document, all
the changes should be applied to other replicas before GC. For this
, if the document is no longer used by this client, it should be
detached.
```

The first line is the subject and should be no longer than 70 characters, the
second line is always blank, and other lines should be wrapped at 80 characters.
This allows the message to be easier to read on GitHub as well as in various git
tools.

### Testing

Testing is the responsibility of all contributors, but it is also coordinated by
maintainers. It is recommended to write them in order from successful cases to
exceptional cases.

There are multiple types of tests. The location of the test code varies with
type, as do the specifics of the environment needed to successfully run the test:

- Unit: These confirm that a particular function behaves as intended. 
- Integration: These tests cover interactions of package components or
 interactions between Yorkie packages and some other non-Yorkie system resource
  (eg: MongoDB, ETCD).
- Benchmark: These confirm that the performance of the implemented function.  

## Contributor License Agreement

We require that all contributors sign our Contributor License Agreement ("CLA") before we can accept the contribution.

### Signing the CLA

Open a pull request ("PR") to any of our open source projects to sign the CLA. A bot will comment on the PR asking you to sign the CLA if you haven't already.

Follow the steps given by the bot to sign the CLA. This will require you to log in with GitHub. We will only use this information for CLA tracking. You only have to sign the CLA once. Once you've signed the CLA, future contributions to the project will not require you to sign again.

### Why Require a CLA?

Agreeing to a CLA explicitly states that you are entitled to provide a contribution, that you cannot withdraw permission to use your contribution at a later date, and that Yorkie Team has permission to use your contribution.

This removes any ambiguities or uncertainties caused by not having a CLA and allows users and customers to confidently adopt our projects. At the same time, the CLA ensures that all contributions to our open source projects are licensed under the project's respective open source license, such as Apache-2.0 License.

Requiring a CLA is a common and well-accepted practice in open source. Major open source projects require CLAs such as Apache Software Foundation projects, Facebook projects, Google projects, Python, Django, and more. Each of these projects remains licensed under permissive OSS licenses such as MIT, Apache, BSD, and more.