Commit message style

This specification is heavily inspired by the AngularJS commit message format.

We have very precise rules over how our Git commit messages must be formatted. This format leads to easier to read commit history.

Each commit message consists of a header, a body (optional), and a footer (optional).

<header>
<BLANK LINE>
<body>
<BLANK LINE>
<footer>

The header is mandatory and must conform to the Commit Message Header format (described below).

The body is mandatory for all commits that are not 100% self explainatory. When the body is present it must be at least 20 characters long and must conform to the Commit Message Body format.

The footer is optional. The Commit Message Footer format (described below) describes what the footer is used for and the structure it must have.

Commit Message Header

<type>(<scope>): <short summary>
  │       │             │
  │       │             └─⫸ Summary in present tense. Not capitalized. No period at the end.
  │       │
  │       └─⫸ Commit Scope: The name of the affected module.
  │
  └─⫸ Commit Type: Build|Docs|Feat|Fix|Perf|Refactor|Test|Merge

The <type> and <summary> fields are mandatory, the (<scope>) field is optional.

type

Must be one of the following:

Build: Changes that affect the build system or external dependencies (example scopes: gulp, broccoli, npm)
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
Test: Adding missing tests or correcting existing tests
Merge: A merging commit

Scope

The scope should be the name of the module affected (as perceived by the person reading the changelog generated from commit messages).

Specify submodules if needed!

Example scopes:

app::events
ui

When a commit affects the whole tree, use treewide.

Summary

Use the summary field to provide 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

Commit Message Body

Just as in the summary, use the imperative, present tense: "fix" not "fixed" nor "fixes".

Explain the motivation for the change in the commit message body. This commit message should explain why you are making the change. You can include a comparison of the previous behavior with the new behavior in order to illustrate the impact of the change.

This is not needed, if the summary is 100% self-explainatory.

Commit Message Footer

The footer can contain information about breaking changes and deprecations and is also the place to reference issues and other PRs that this commit closes or is related to. For example:

BREAKING CHANGE: <breaking change summary>
<BLANK LINE>
<breaking change description + migration instructions>
<BLANK LINE>
<BLANK LINE>
Fixes #<issue number>

DEPRECATED: <what is deprecated>
<BLANK LINE>
<deprecation description + recommended update path>
<BLANK LINE>
<BLANK LINE>
Closes #<pr number>

Breaking Change section should start with the phrase "BREAKING CHANGE: " followed by a summary of the breaking change, a blank line, and a detailed description of the breaking change that also includes migration instructions.

Similarly, a Deprecation section should start with "DEPRECATED: " followed by a short description of what is deprecated, a blank line, and a detailed description of the deprecation that also mentions the recommended update path.

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