Commitlint

<!-- Copyright 2025-2026 Richard Shade. Licensed under Apache-2.0. --> <!-- SPDX-License-Identifier: Apache-2.0 -->

Commitlint

Validate commit messages follow the Conventional Commits specification. Enables automatic changelog generation, semantic versioning, and clean git history.

What this skill does

1. Checks if @commitlint/cli and @commitlint/config-conventional are installed; installs them if missing.
2. Detects project-specific commitlint configuration or falls back to a sensible default config.
3. Validates commit messages for type, scope, subject, body, and footer format.
4. Reports errors with specific fixes and examples.

Installation check

# Check if commitlint is available
npx commitlint --version 2>/dev/null

If not installed, install globally:

npm install -g @commitlint/cli @commitlint/config-conventional

If installation fails (permissions, no npm), stop validation and report the issue with remediation steps:

• Use sudo npm install -g ... or fix npm permissions
• Use a Node version manager (nvm, volta, fnm)
• Install Node.js if not present

Do not silently skip validation.

Config detection priority

1. commitlint.config.js in project root
2. .commitlintrc.json in project root
3. .commitlintrc.yaml in project root
4. .commitlintrc in project root
5. commitlint field in package.json
6. Default config (see references/conventional-commits.md)

If no project config exists, create a temporary .commitlintrc.json using the default config from the reference document before running validation.

Validation workflow

1. Check commitlint installation
   ├─ Installed → continue
   └─ Missing → install, then continue (fail if install fails)

2. Detect project config
   ├─ Found → use it
   └─ Not found → use default config from references/

3. Run validation
   ├─ From a string:
   │    echo "<message>" | npx commitlint
   ├─ From a file:
   │    cat <file> | npx commitlint
   └─ From last git commit:
        git log -1 --format=%B | npx commitlint

4. Report results
   ├─ Valid → confirm and proceed
   └─ Invalid → show errors, suggest fixes, re-validate after correction

Validation methods

Validate a commit message string

echo "feat(api): add login endpoint" | npx commitlint

Validate contents of a file

cat path/to/message-file.txt | npx commitlint

Validate the most recent git commit

git log -1 --format=%B | npx commitlint

Error handling

Install failure

If commitlint cannot be installed, report the error and provide remediation steps. Do not proceed with validation.

Invalid message

When validation fails, report each error with:

• The rule that failed (e.g., type-enum, header-max-length)
• What was wrong (e.g., type feature is not allowed)
• A concrete fix (e.g., use feat instead)

Example:

Validation failed:

1. type-enum: type 'feature' is not allowed
   Allowed: feat, fix, docs, style, refactor, perf, test, build, ci,
            chore, revert
   Fix: use 'feat' instead of 'feature'

2. header-max-length: header is 72 characters (max 50)
   Fix: shorten to 'feat: add user authentication with JWT'

After reporting errors, suggest a corrected message and re-validate.

Format reference

See references/conventional-commits.md for the full Conventional Commits format specification, type descriptions, rules, default config, and examples.