# Contribute to PaddlePaddle

We sincerely appreciate your contributions. You can use fork and pull request
workflow to merge your code. 
 
## Code Requirements
- Your code mush be fully documented by
  [doxygen](http://www.stack.nl/~dimitri/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](https://help.github.com/articles/fork-a-repo/)
 
Just head over to the GitHub page and click the "Fork" button.
It's just that simple. 

## Clone

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:
 
```shell
# Clone your fork to your local machine
git clone https://github.com/USERNAME/Paddle.git
```
Then you can start to develop by making a local developement branch
```shell
git checkout -b MY_COOL_STUFF_BRANCH origin/master
```

## Commit

Commit your changes by following command lines:

```shell
# show the working tree status
git status
# add modified files
git add xx
git commit -m "commit info"
```
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:

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

Update your fork with the latest upstream changes:

```shell
git pull --rebase upstream HEAD
```

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

```shell
# push to your repository in Github
git push origin HEAD
```

## 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:
```shell
git checkout MY_COOL_STUFF_BRANCH
git pull --rebase upstream HEAD
# You may need to resolve the conflict according to the git prompt.
# Make and test your code.
git push -f origin HEAD
```
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.