# Contributing to PowerShell

We welcome and appreciate contributions from the community.
There are many ways to become involved with PowerShell:
including filing issues,
joining in design conversations,
writing and improving documentation,
and contributing to the code.
Please read the rest of this document to ensure a smooth contribution process.

## Intro to Git and GitHub

* Make sure you have a [GitHub account](https://github.com/signup/free).
* Learning Git:
  * GitHub Help: [Good Resources for Learning Git and GitHub][good-git-resources]
  * [Git Basics](../docs/git/basics.md): install and getting started
* [GitHub Flow Guide](https://guides.github.com/introduction/flow/):
  step-by-step instructions of GitHub Flow

## Quick Start Checklist

* Review the [Contribution License Agreement][CLA] requirement.
* Get familiar with the [PowerShell repository](../docs/git).

## Contributing to Issues

* Review [Issue Management][issue-management].
* Check if the issue you are going to file already exists in our [GitHub issues][open-issue].
* If you can't find your issue already,
  [open a new issue](https://github.com/PowerShell/PowerShell/issues/new),
  making sure to follow the directions as best you can.
* If the issue is marked as [`Up-for-Grabs`][up-for-grabs],
  the PowerShell Maintainers are looking for help with the issue.

## Contributing to Documentation

### Contributing to documentation related to PowerShell

Please see the [Contributor Guide in `PowerShell/PowerShell-Docs`](https://github.com/PowerShell/PowerShell-Docs/blob/staging/CONTRIBUTING.md).

### Contributing to documentation related to maintaining or contributing to the PowerShell project

* When writing Markdown documentation, use [semantic linefeeds][].
  In most cases, it means "one clause/idea per line".
* Otherwise, these issues should be treated like any other issue in this repo.

#### Spellchecking documentation

Documentation are spellchecked. We make use of the
[markdown-spellcheck](https://github.com/lukeapage/node-markdown-spellcheck) command line tool,
which can be run in interactive mode to correct typos or add words to the ignore list
(`.spelling` at the repository root).

To run the spellchecker, follow the steps as follows:

* install [Node.js](https://nodejs.org/en/) (v6.4.0 or up)
* install [markdown-spellcheck](https://github.com/lukeapage/node-markdown-spellcheck) by
  `npm install -g markdown-spellcheck` (v0.11.0 or up)
* run `mdspell "**/*.md" --ignore-numbers --ignore-acronyms`
* if the `.spelling` file is updated, commit and push it

## Contributing to Code

### Code Editor

You should use the multi-platform [Visual Studio Code (VS Code)][use-vscode-editor].

### Building and testing

#### Building PowerShell

Please see [Building PowerShell](../README.md#building-the-repository).

#### Testing PowerShell

Please see PowerShell [Testing Guidelines - Running Tests Outside of CI][running-tests-outside-of-ci] on how to test you build locally.

### Finding or creating an issue

1. Follow the instructions in [Contributing to Issues][contribute-issues] to find or open an issue.
1. Mention in the issue that you are working on the issue and ask `@powershell/powershell` for an assignment.

### Forks and Pull Requests

GitHub fosters collaboration through the notion of [pull requests][using-prs].
On GitHub, anyone can [fork][fork-a-repo] an existing repository
into their own user account, where they can make private changes to their fork.
To contribute these changes back into the original repository,
a user simply creates a pull request in order to "request" that the changes be taken "upstream".

Additional references:

* GitHub's guide on [forking](https://guides.github.com/activities/forking/)
* GitHub's guide on [Contributing to Open Source](https://guides.github.com/activities/contributing-to-open-source/#pull-request)
* GitHub's guide on [Understanding the GitHub Flow](https://guides.github.com/introduction/flow/)

### Lifecycle of a pull request

#### Before submitting

* To avoid merge conflicts, make sure your branch is rebased on the `master` branch of this repository.
* Many code changes will require new tests,
  so make sure you've added a new test if existing tests do not effectively test the code changed.
* Clean up your commit history.
  Each commit should be a **single complete** change.
  This discipline is important when reviewing the changes as well as when using `git bisect` and `git revert`.

#### Pull request submission

**Always create a pull request to the `master` branch of this repository**.

![Github-PR-dev.png](Images/Github-PR-dev.png)

* If you're contributing in a way that changes the user or developer experience, you are expected to document those changes.
  See [Contributing to documentation related to PowerShell](#contributing-to-documentation-related-to-powershell).
* Add a meaningful title of the PR describing what change you want to check in.
  Don't simply put: "Fixes issue #5".
  A better example is: "Add Ensure parameter to New-Item cmdlet", with "Fixes #5" in the PR's body.
* When you create a pull request,
  including a summary of what's included in your changes and
  if the changes are related to an existing GitHub issue,
  please reference the issue in pull request description (e.g. ```Closes #11```).
  See [this][closing-via-message] for more details.
* If the change warrants a note in the [changelog](../CHANGELOG.MD)
  either update the changelog in your pull request or
  add a comment in the PR description saying that the change may warrant a note in the changelog.
  New changes always go into the **Unreleased** section.
  Keeping the changelog up-to-date simplifies the release process for Maintainers.
  An example (with an associated PR #):

  ```markdown
  Unreleased
  ----------

  * `Update-Item` now supports `-FriendlyName` (#1234).
  ```

* Please use the present tense and imperative mood when describing your changes:
  * Instead of "Adding support for Windows Server 2012 R2", write "Add support for Windows Server 2012 R2".
  * Instead of "Fixed for server connection issue", write "Fix server connection issue".

  This form is akin to giving commands to the code base
  and is recommended by the Git SCM developers.
  It is also used in the [Git commit messages](#common-engineering-practices).
* If the change is related to a specific resource, please prefix the description with the resource name:
  * Instead of "New parameter 'ConnectionCredential' in New-SqlConnection",
  write "New-SqlConnection: add parameter 'ConnectionCredential'".
* If your change warrants an update to user-facing documentation,
  a Maintainer will add the `Documentation Needed` label to your PR and add an issue to the [PowerShell-Docs repository][PowerShell-Docs],
  so that we make sure to update official documentation to reflect your contribution.
  As an example, this requirement includes any changes to cmdlets (including cmdlet parameters) and features which have associated about_* topics.
  While not required, we appreciate any contributors who add this label and create the issue themselves.
  Even better, all contributors are free to contribute the documentation themselves.
  (See [Contributing to documentation related to PowerShell](#contributing-to-documentation-related-to-powershell) for more info.)

#### Pull Request - Automatic Checks

* If this is your first contribution to PowerShell,
  you may be asked to sign a [Contribution Licensing Agreement][CLA] (CLA)
  before your changes will be accepted.
* Make sure you follow the [Common Engineering Practices](#common-engineering-practices)
  and [testing guidelines](../docs/testing-guidelines/testing-guidelines.md).
* After submitting your pull request,
  our [CI system (Travis CI and AppVeyor)][ci-system]
  will run a suite of tests and automatically update the status of the pull request.
* Our CI contains automated spellchecking. If there is any false-positive,
  [run the spellchecker command line tool in interactive mode](#spellchecking-documentation)
  to add words to the `.spelling` file.

#### Pull Request - Code Review

* Roles and Responsibilities of a PR: Author, Reviewer, and Assignee
  * Reviewer and Assignee are two separate roles of a PR.
    * A Reviewer can be anyone who wants to contribute.
      A Reviewer reviews the change of a PR,
      leaves comments for the Author to address,
      and approves the PR when the change looks good.
    * An Assignee must be a [Maintainer](../docs/maintainers), who monitors the progress of the PR,
      coordinates the review process, and merges the PR after it's been approved.
      The Assignee may or may not be a Reviewer of the PR at the same time.
  * An Author is encouraged to choose Reviewer(s) and an Assignee for the PR.
    If no Assignee is chosen, one of the Maintainers shall be assigned to it.
    If no Reviewer is chosen, the Assignee shall choose Reviewer(s) as appropriate.
    * If an Author is a [PowerShell Team](https://github.com/orgs/PowerShell/people) member,
      then the Author **is required** to choose Reviewer(s) and an Assignee for the PR.
  * For a PR to be merged, it must be approved by at least one PowerShell Team member or Collaborator,
    so additional Reviewer(s) may be added by the Assignee as appropriate.
    The Assignee may also be re-assigned by Maintainers.
* A Reviewer can postpone the code review if CI builds fail,
  but also can start the code review early regardless of the CI builds.
* The Author **is responsible** for driving the PR to the Approved state.
  The Author addresses review comments, and pings Reviewer(s) to start the next iteration.
  If the review is making no progress (or very slow),
  the Author can always ask the Assignee to help coordinate the process and keep it moving.
* Additional feedback is always welcome!
  Even if you are not designated as a Reviewer,
  feel free to review others' pull requests anyway.
  Leave your comments even if everything looks good;
  a simple "Looks good to me" or "LGTM" will suffice.
  This way we know someone has already taken a look at it!
* When updating your pull request, please **create new commits**
  and **don't rewrite the commits history**. This way it's very easy for
  the reviewers to see diff between iterations.
  If you rewrite the history in the pull request, review could be much slower.
  Once the review is done, you can rewrite the history to make it prettier,
  if you like.
  Otherwise it's likely would be squashed on merge to master.
* Once the code review is done,
  all merge conflicts are resolved,
  and the CI system build status is passing,
  the PR Assignee will merge your changes.
* For more information on the PowerShell Maintainers' process,
  see the [documentation](../docs/maintainers).

## Making Breaking Changes

When you make code changes,
please pay attention to these that can affect the [Public Contract](../docs/dev-process/breaking-change-contract.md).
For example, changing PowerShell parameters, APIs, or protocols break the public contract.
Before making changes to the code,
first review the [breaking changes contract](../docs/dev-process/breaking-change-contract.md)
and follow the guidelines to keep PowerShell backward compatible.

## Making Design Changes

To add new features such as cmdlets or making design changes,
please follow the [PowerShell Request for Comments (RFC)](https://github.com/PowerShell/PowerShell-RFC) process.

## Common Engineering Practices

Other than the guidelines for ([coding](../docs/dev-process/coding-guidelines.md),
the [RFC process](https://github.com/PowerShell/PowerShell-RFC) for design,
[documentation](#contributing-to-documentation) and [testing](../docs/testing-guidelines/testing-guidelines.md)) discussed above,
we encourage contributors to follow these common engineering practices:

* Format commit messages following these guidelines:

```
Summarize change in 50 characters or less

Similar to email, this is the body of the commit message,
and the above is the subject.
Always leave a single blank line between the subject and the body
so that `git log` and `git rebase` work nicely.

The subject of the commit should use the present tense and
imperative mood, like issuing a command:

> Makes abcd do wxyz

The body should be a useful message explaining
why the changes were made.

If significant alternative solutions were available,
explain why they were discarded.

Keep in mind that the person most likely to refer to your commit message
is you in the future, so be detailed!

As Git commit messages are most frequently viewed in the terminal,
you should wrap all lines around 72 characters.

Using semantic line feeds (breaks that separate ideas)
is also appropriate, as is using Markdown syntax.
```

* These are based on Tim Pope's [guidelines](http://tbaggery.com/2008/04/19/a-note-about-git-commit-messages.html),
  Git SCM [submitting patches](https://git.kernel.org/cgit/git/git.git/tree/Documentation/SubmittingPatches),
  Brandon Rhodes' [semantic linefeeds][],
  and John Gruber's [Markdown syntax](https://daringfireball.net/projects/markdown/syntax).
* Don't commit code that you didn't write.
  If you find code that you think is a good fit to add to PowerShell,
  file an issue and start a discussion before proceeding.
* Create and/or update tests when making code changes.
* Run tests and ensure they are passing before pull request.
* All pull requests **must** pass CI systems before they can be approved.
* Avoid making big pull requests.
  Before you invest a large amount of time,
  file an issue and start a discussion with the community.

## Contributor License Agreement (CLA)

To speed up the acceptance of any contribution to any PowerShell repositories,
you could [sign a Microsoft Contribution Licensing Agreement (CLA)](https://cla.microsoft.com/) ahead of time.
If you've already contributed to PowerShell repositories in the past, congratulations!
You've already completed this step.
This a one-time requirement for the PowerShell project.
Signing the CLA process is simple and can be done in less than a minute.
You don't have to do this up-front.
You can simply clone, fork, and submit your pull request as usual.
When your pull request is created, it is classified by a CLA bot.
If the change is trivial, it's classified as `cla-required`.
Once you sign a CLA, all your existing and future pull requests will be labeled as `cla-signed`.

[testing-guidelines]: ../docs/testing-guidelines/testing-guidelines.md
[running-tests-outside-of-ci]: ../docs/testing-guidelines/testing-guidelines.md#running-tests-outside-of-ci
[issue-management]: ../docs/maintainers/issue-management.md
[governance]: ../docs/community/governance.md
[using-prs]: https://help.github.com/articles/using-pull-requests/
[fork-a-repo]: https://help.github.com/articles/fork-a-repo/
[closing-via-message]: https://help.github.com/articles/closing-issues-via-commit-messages/
[CLA]: #contributor-license-agreement-cla
[ci-system]: ../docs/testing-guidelines/testing-guidelines.md#ci-system
[good-git-resources]: https://help.github.com/articles/good-resources-for-learning-git-and-github/
[contribute-issues]: #contributing-to-issues
[open-issue]: https://github.com/PowerShell/PowerShell/issues
[up-for-grabs]: https://github.com/powershell/powershell/issues?q=is%3Aopen+is%3Aissue+label%3AUp-for-Grabs
[semantic linefeeds]: http://rhodesmill.org/brandon/2012/one-sentence-per-line/
[PowerShell-Docs]: https://github.com/powershell/powershell-docs/
[use-vscode-editor]: ../docs/learning-powershell/using-vscode.md#editing-with-visual-studio-code
