# Contributing

We'd love to accept your patches and contributions to Pigweed. There are just a
few small guidelines you need to follow. Before making or sending major changes,
please reach out on the [mailing list](mailto:pigweed@googlegroups.com) first to
ensure the changes make sense for upstream. We generally go through a design
phase before making large changes.

Before participating in our community, please take a moment to review our [code
of conduct](CODE_OF_CONDUCT.md). We expect everyone who interacts with the
project to respect these guidelines.

Pigweed contribution overview:
 1. One-time contributor setup:
   * Sign the [Contributor License Agreement](https://cla.developers.google.com/).
   * Verify that Git user email (git config user.email) is either Google Account
     email or an Alternate email for the Google account used to sign the CLA (Manage
     Google account->Personal Info->email).
   * Install the [Gerrit commit hook](CONTRIBUTING.md#gerrit-commit-hook) to
     automatically add a `Change-Id: ...` line to your commit.
   * Install the Pigweed presubmit check hook (`pw presubmit --install`).
     (recommended).
 1. Ensure all files include a correct [copyright and license header](CONTRIBUTING.md#source-code-headers).
 1. Run `pw presubmit` (see below) to detect style or compilation issues before
    uploading.
 1. Upload the change with `git push origin HEAD:refs/for/master`.
 1. Address any reviewer feedback by amending the commit (`git commit --amend`).
 1. Submit change to CI builders to merge. If you are not part of Pigweed's
    core team, you can ask the reviewer to add the `+2 CQ` vote, which will
    trigger a rebase asd submit once the builders pass.

## Contributor License Agreement

Contributions to this project must be accompanied by a Contributor License
Agreement. You (or your employer) retain the copyright to your contribution;
this simply gives us permission to use and redistribute your contributions as
part of the project. Head over to <https://cla.developers.google.com/> to see
your current agreements on file or to sign a new one.

You generally only need to submit a CLA once, so if you've already submitted one
(even if it was for a different project), you probably don't need to do it
again.

## Gerrit Commit Hook

Gerrit requires all changes to have a `Change-Id` tag at the bottom of each CL.
You should set this up to be done automatically using the instructions below.

**Linux/macOS**<br/>
```bash
$ f=`git rev-parse --git-dir`/hooks/commit-msg ; mkdir -p $(dirname $f) ; curl -Lo $f https://gerrit-review.googlesource.com/tools/hooks/commit-msg ; chmod +x $f
```

**Windows**<br/>
Download [the Gerrit commit hook](https://gerrit-review.googlesource.com/tools/hooks/commit-msg)
and then copy it to the `.git\hooks` directory in the Pigweed repository.
```batch
copy %HOMEPATH%\Downloads\commit-msg %HOMEPATH%\pigweed\.git\hooks\commit-msg
```

## Code Reviews

All Pigweed development happens on Gerrit, following the [typical Gerrit
development workflow](http://ceres-solver.org/contributing.html). Consult
[Gerrit User Guide](https://gerrit-documentation.storage.googleapis.com/Documentation/2.12.3/intro-user.html)
for more information on using Gerrit.

In the future we may support GitHub pull requests, but until that time we will
close GitHub pull requests and ask that the changes be uploaded to Gerrit
instead.

## Community Guidelines

This project follows [Google's Open Source Community
Guidelines](https://opensource.google/conduct/) and the [Pigweed Code of
Conduct](CODE_OF_CONDUCT.md).

## Source Code Headers

Every Pigweed file containing source code must include copyright and license
information. This includes any JS/CSS files that you might be serving out to
browsers.

Apache header for C and C++ files:

```javascript
// Copyright 2020 The Pigweed Authors
//
// Licensed under the Apache License, Version 2.0 (the "License"); you may not
// use this file except in compliance with the License. You may obtain a copy of
// the License at
//
//     https://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
// WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
// License for the specific language governing permissions and limitations under
// the License.
```

Apache header for Python and GN files:

```python
# Copyright 2020 The Pigweed Authors
#
# Licensed under the Apache License, Version 2.0 (the "License"); you may not
# use this file except in compliance with the License. You may obtain a copy of
# the License at
#
#     https://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
# WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
# License for the specific language governing permissions and limitations under
# the License.
```

## Continuous Integration

All Pigweed CLs must adhere to Pigweed's style guide and pass a suite of
automated builds, tests, and style checks to be merged upstream. Much of this
checking is done using Pigweed's pw_presubmit module by automated builders. To
speed up the review process, consider adding `pw presubmit` as a git push hook
using the following command:

**Linux/macOS**<br/>
```bash
$ pw presubmit --install
```

This will be effectively the same as running the following command before every
`git push`:
```bash
$ pw presubmit --program quick
```

![pigweed presubmit demonstration](docs/images/pw_presubmit_demo.gif)

Running `pw presubmit` manually will default to running the `full` presubmit
program.

If you ever need to bypass the presubmit hook (due to it being broken, for example) you
may push using this command:

```bash
$ git push origin HEAD:refs/for/master --no-verify
```