# Contribute Code

We sincerely appreciate your contributions. You can use fork and pull request workflow to merge your code.

## Code Requirements

- Your code must be fully documented by doxygen style.
- Make sure the compiler option WITH_STYLE_CHECK is on and the compiler passes the code style check.
- All code must have unit test.
- Pass all unit tests.

The following tutorial guides you into submitting your contibution.

## Creating a Fork

Just head over to the GitHub page and click the “Fork” button. It’s just that simple.

## Clone

Paddle is currently using git-flow branching model. The develop is the main branch, and other user’s branches are feature branches.

Once you’ve created a fork, you can use your favorite git client to clone your repo or just head straight to the command line:

    # Clone your fork to your local machine
    git clone --branch develop https://github.com/USERNAME/Paddle.git

If your repository doesn’t contain develop branch, just create it by your own.

    git clone https://github.com/USERNAME/Paddle.git Paddle
    cd Paddle
    git checkout -b develop  # create develop branch.
    git remote add upstream https://github.com/PaddlePaddle/Paddle.git  # add upstream to baidu/Paddle
    git pull upstream develop  # update to upstream

Then you can start to develop by making a local developement branch

    git checkout -b MY_COOL_STUFF_BRANCH

## Using `pre-commit` hook

Paddle developers use pre-commit tool to manage git pre-commit hooks. It can help us format source codes (cpp, python), check some basic thing before commit (only one EOL for each file, do not add a huge file in git). `pre-commit` tests is a part of unit tests in Travis-CI now, every PR doesn’t fit hook can not be merged into Paddle.

To use pre-commit, you should install it by `pip install pre-commit`, and currently, Paddle uses `clang-format` to format c/cpp sources. Please make sure clang-format 3.8+ installed.

Then just run `pre-commit install` in your Paddle clone directory. When you commit your code, the pre-commit hook will check the local code if there is anything not suitable to commit, and so on.

## Commit

Commit your changes by following command lines:

    # show the working tree status
    git status
    # add modified files
    git add xx
    env EDITOR=vim git commit  # You can write your comments by vim/nano/emacs.

The first line of commit infomation is the title. The second and later lines are the details if any.

## Keeping Fork Up to Date

Before pull your request, you should sync your code from the latest PaddlePaddle. To do this, you’ll need to add a remote at first:

    # see the current configured remote repository
    git remote -v
    # add upstream repository
    git remote add upstream https://github.com/PaddlePaddle/Paddle.git
    # verify the new upstream
    git remote -v

Update your fork with the latest upstream changes:

    git pull --rebase upstream develop

If there are no unique commits locally, git will simply perform a fast-forward. However, if you have been making changes (in the vast majority of cases you probably shouldn’t be), you may have to deal with conflicts.

Now, your local master branch is up-to-date with everything modified upstream.

## Push to GitHub

    # push to your repository in Github
    git push -u origin MY_COOL_STUFF_BRANCH  # create remote branch MY_COOL_STUFF_BRANCH to origin.

## Pull Request

Go to the page for your fork on GitHub, select your development branch, and click the pull request button.

## Update your pull request with the lastest version

During the code review, your pull request may become stale because new commits in baidu/Paddle. GitHub allows autmotic update if there is no conflict. You can do this by clicking the “Update Branch” button in your pull request page. However, in the case of conflict, you need to do the update manually. You need to do the following on your local repository:

    git checkout MY_COOL_STUFF_BRANCH
    git pull upstream develop
    # You may need to resolve the conflict according to the git prompt.
    # Make and test your code.
    git push origin MY_COOL_STUFF_BRANCH

Now your Pull Request is updated with the latest version.

## Revise your pull request

When you revise your pull request according to reviewer’s comments, please use ‘git commit’ instead of ‘git commit –amend’ to commit your changes so that the reviewers can see the difference between the new pull requrest and the old pull request.

The possible commands are

    git checkout MY_COOL_STUFF_BRANCH
    git pull upstream develop   # update local to newest code base.
    # May be some conflicts will occured.
    # And develop your cool stuff
    env EDITOR=vim git commit  # add your revise log
    git push origin MY_COOL_STUFF_BRANCH