# Contributing to Docker

Want to hack on Docker? Awesome! Here are instructions to get you started. They are probably not perfect, please let us know if anything feels
wrong or incomplete.

## Contribution guidelines

### Pull requests are always welcome

We are always thrilled to receive pull requests, and do our best to
process them as fast as possible. Not sure if that typo is worth a pull
request? Do it! We will appreciate it.

If your pull request is not accepted on the first try, don't be
discouraged! If there's a problem with the implementation, hopefully you
received feedback on what to improve.

We're trying very hard to keep Docker lean and focused. We don't want it
to do everything for everybody. This means that we might decide against
incorporating a new feature. However, there might be a way to implement
that feature *on top of* docker.

### Discuss your design on the mailing list

We recommend discussing your plans [on the mailing
list](https://groups.google.com/forum/?fromgroups#!forum/docker-club)
before starting to code - especially for more ambitious contributions.
This gives other contributors a chance to point you in the right
direction, give feedback on your design, and maybe point out if someone
else is working on the same thing.

### Create issues...

Any significant improvement should be documented as [a github
issue](https://github.com/dotcloud/docker/issues) before anybody
starts working on it.

### ...but check for existing issues first!

Please take a moment to check that an issue doesn't already exist
documenting your bug report or improvement proposal. If it does, it
never hurts to add a quick "+1" or "I have this problem too". This will
help prioritize the most common problems and requests.

### Conventions

Fork the repo and make changes on your fork in a feature branch:

- If it's a bugfix branch, name it XXX-something where XXX is the number of the
  issue
- If it's a feature branch, create an enhancement issue to announce your
  intentions, and name it XXX-something where XXX is the number of the issue.

Submit unit tests for your changes.  Go has a great test framework built in; use
it! Take a look at existing tests for inspiration. Run the full test suite on
your branch before submitting a pull request.

Make sure you include relevant updates or additions to documentation when
creating or modifying features.

Write clean code. Universally formatted code promotes ease of writing, reading,
and maintenance. Always run `go fmt` before committing your changes. Most
editors have plugins that do this automatically, and there's also a git
pre-commit hook:

```
curl -o .git/hooks/pre-commit https://raw.github.com/edsrzf/gofmt-git-hook/master/fmt-check && chmod +x .git/hooks/pre-commit
```

Pull requests descriptions should be as clear as possible and include a
reference to all the issues that they address.

Code review comments may be added to your pull request. Discuss, then make the
suggested modifications and push additional commits to your feature branch. Be
sure to post a comment after pushing. The new commits will show up in the pull
request automatically, but the reviewers will not be notified unless you
comment.

Before the pull request is merged, make sure that you squash your commits into
logical units of work using `git rebase -i` and `git push -f`. After every
commit the test suite should be passing. Include documentation changes in the
same commit so that a revert would remove all traces of the feature or fix.

Commits that fix or close an issue should include a reference like `Closes #XXX`
or `Fixes #XXX`, which will automatically close the issue when merged.

Add your name to the AUTHORS file, but make sure the list is sorted and your
name and email address match your git configuration. The AUTHORS file is
regenerated occasionally from the git commit history, so a mismatch may result
in your changes being overwritten.


## Decision process

### How are decisions made?

Short answer: with pull requests to the docker repository.

Docker is an open-source project with an open design philosophy. This means that the repository is the source of truth for EVERY aspect of the project,
including its philosophy, design, roadmap and APIs. *If it's part of the project, it's in the repo. It's in the repo, it's part of the project.*

As a result, all decisions can be expressed as changes to the repository. An implementation change is a change to the source code. An API change is a change to
the API specification. A philosophy change is a change to the philosophy manifesto. And so on.

All decisions affecting docker, big and small, follow the same 3 steps:

* Step 1: Open a pull request. Anyone can do this.

* Step 2: Discuss the pull request. Anyone can do this.

* Step 3: Accept or refuse a pull request. The relevant maintainer does this (see below "Who decides what?")


### Who decides what?

So all decisions are pull requests, and the relevant maintainer makes the decision by accepting or refusing the pull request.
But how do we identify the relevant maintainer for a given pull request?

Docker follows the timeless, highly efficient and totally unfair system known as [Benevolent dictator for life](http://en.wikipedia.org/wiki/Benevolent_Dictator_for_Life),
with yours truly, Solomon Hykes, in the role of BDFL.
This means that all decisions are made by default by me. Since making every decision myself would be highly unscalable, in practice decisions are spread across multiple maintainers.

The relevant maintainer for a pull request is assigned in 3 steps:

* Step 1: Determine the subdirectory affected by the pull request. This might be src/registry, docs/source/api, or any other part of the repo.

* Step 2: Find the MAINTAINERS file which affects this directory. If the directory itself does not have a MAINTAINERS file, work your way up the the repo hierarchy until you find one.

* Step 3: The first maintainer listed is the primary maintainer. The pull request is assigned to him. He may assign it to other listed maintainers, at his discretion.


### I'm a maintainer, should I make pull requests too?

Primary maintainers are not required to create pull requests when changing their own subdirectory, but secondary maintainers are.

### Who assigns maintainers?

Solomon.

### How can I become a maintainer?

* Step 1: learn the component inside out
* Step 2: make yourself useful by contributing code, bugfixes, support etc.
* Step 3: volunteer on the irc channel (#docker@freenode)

Don't forget: being a maintainer is a time investment. Make sure you will have time to make yourself available.
You don't have to be a maintainer to make a difference on the project!

### What are a maintainer's responsibility?

It is every maintainer's responsibility to:

* 1) Expose a clear roadmap for improving their component.
* 2) Deliver prompt feedback and decisions on pull requests.
* 3) Be available to anyone with questions, bug reports, criticism etc. on their component. This includes irc, github requests and the mailing list.
* 4) Make sure their component respects the philosophy, design and roadmap of the project.

### How is this process changed?

Just like everything else: by making a pull request :)