# Contributing

## Commit Message Guidelines

We have very precise rules over how our git commit messages can be formatted.  This leads to **more
readable messages** that are easy to follow when looking through the **project history**.

### Commit Message Format

Each commit message consists of a **header**, a **body** and a **footer**.  The header has a special
format that includes a **type**, a **scope** and a **subject**:

```txt
<type>(<scope>): <subject>
<BLANK LINE>
<body>
<BLANK LINE>
<footer>
```

The **header** is mandatory and the **scope** of the header is optional.

Any line of the commit message cannot be longer 100 characters! This allows the message to be easier
to read on GitHub as well as in various git tools.

The footer should contain a [closing reference to an issue](https://help.github.com/articles/closing-issues-via-commit-messages/) if any.

```txt
docs(changelog): update changelog to beta.5
```

```txt
fix(release): need to depend on latest rxjs and zone.js

The version in our package.json gets copied to the one we publish, and users need the latest of these.
```

### Revert

If the commit reverts a previous commit, it should begin with `revert: `, followed by the header of the reverted commit. In the body it should say: `This reverts commit <hash>.`, where the hash is the SHA of the commit being reverted.

### Type

Must be one of the following:

* **build**: Changes that affect the build system or external dependencies (example scopes: crypto, wot)
* **chore**: Modification of the repository architecture
* **ci**: Changes to our CI configuration files and scripts (example scopes: Github Actions, Gitlab CI)
* **docs**: Documentation only changes
* **feat**: A new feature
* **fix**: A bug fix
* **perf**: A code change that improves performance
* **refactor**: A code change that neither fixes a bug nor adds a feature
* **style**: Changes that do not affect the meaning of the code (white-space, formatting, missing semi-colons, etc)
* **test**: Adding missing tests or correcting existing tests

### Subject

The subject contains a succinct description of the change:

* use the imperative, present tense: "change" not "changed" nor "changes"
* don't capitalize the first letter
* no dot (.) at the end

### Body

Just as in the **subject**, use the imperative, present tense: "change" not "changed" nor "changes".
The body should include the motivation for the change and contrast this with previous behavior.

### Footer

The footer should contain any information about **Breaking Changes** and is also the place to
reference issues that this commit **Closes**.

**Breaking Changes** should start with the word `BREAKING CHANGE:` with a space or two newlines. The rest of the commit message is then used for this.
