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Commit Messages

Context and Problem Statement

Based on the decision to use Semantic Versioning, we have to decide how to identify breaking changes and how to determine the version for a component ?

Decision Drivers

  • Usability for the developers.
  • Ability to easily identify commits containing new features and breaking changes.
  • Ability to generate a changelog of the changes and the associated version.
  • Availability of GitLab CI Pipeline templates within Siemens.
  • Availability of syntax checks.

Considered Options

Decision Outcome

Chosen option: "Angular Commit Message convention" because,

  • This option was chosen because it provides the best usability for the developers combined with a broad tool support.
  • In addition, changelogs can be generated automatically when following these rules.

Pros and Cons of the Options

Angular Commit Message convention

Positive:

  • CHANGELOGs can be generated automatically
  • semantic version bumps can be determined automatically based on the types of commits landed
  • the nature of changes can be communicated to teammates, the public, and other stakeholders
  • build and publish processes can be triggered
  • the commit history is more structured and easier to explore
  • deprecations can be communicated easier

Negative:

  • strict rules have to be followed
  • tool to check these rules must be selected

More Information

Rules to follow

  1. Commits MUST be prefixed with a type, which consists of a noun, feat, fix, etc., followed by the OPTIONAL scope, OPTIONAL !, and REQUIRED terminal colon and space.
  2. The type feat MUST be used when a commit adds a new feature to your application or library.
  3. The type fix MUST be used when a commit represents a bug fix for your application.
  4. A scope MAY be provided after a type. A scope MUST consist of a noun describing a section of the codebase surrounded by parenthesis, e.g., fix(parser):
  5. A description MUST immediately follow the colon and space after the type/scope prefix. The description is a short summary of the code changes, e.g., fix: array parsing issue when multiple spaces were contained in string.
  6. A longer commit body MAY be provided after the short description, providing additional contextual information about the code changes. The body MUST begin one blank line after the description.
  7. A commit body is free-form and MAY consist of any number of newline separated paragraphs.
  8. One or more footers MAY be provided one blank line after the body. Each footer MUST consist of a word token, followed by either a : or # separator, followed by a string value (this is inspired by the git trailer convention).
  9. A footer’s token MUST use - in place of whitespace characters, e.g., Acked-by (this helps differentiate the footer section from a multi-paragraph body). An exception is made for BREAKING CHANGE, which MAY also be used as a token.
  10. A footer’s value MAY contain spaces and newlines, and parsing MUST terminate when the next valid footer token/separator pair is observed.
  11. Breaking changes MUST be indicated in the type/scope prefix of a commit, or as an entry in the footer.
  12. If included as a footer, a breaking change MUST consist of the uppercase text BREAKING CHANGE, followed by a colon, space, and description, e.g., BREAKING CHANGE: environment variables now take precedence over config files.
  13. If included in the type/scope prefix, breaking changes MUST be indicated by a ! immediately before the :. If ! is used, BREAKING CHANGE: MAY be omitted from the footer section, and the commit description SHALL be used to describe the breaking change.
  14. Types other than feat and fix MAY be used in your commit messages, e.g., docs: update ref docs.
  15. The units of information that make up Conventional Commits MUST NOT be treated as case sensitive by implementors, with the exception of BREAKING CHANGE which MUST be uppercase.
  16. BREAKING-CHANGE MUST be synonymous with BREAKING CHANGE, when used as a token in a footer.

Type: MUST be one of the following: - build: Changes that affect the build system - chore: A code change that external user won't see (e.g., dev dependencies updated by Renovate Bot or a change to .gitignore file) - ci: Changes to our CI configuration files and scripts - 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 - revert: A revert of a commit - style: A code that is related to styling - test: Adding missing test or correcting existing tests

Scope: To update dependencies, the scope deps SHALL be used (e.g., Renovate Bot).

If additional scopes are used, they MUST be defined in the CONTRIBUTING.md file of the git repository.