Semantic versioning enforcement with commitlint in CI

Teams adopt conventional commits informally but inconsistently. Commits like 'fix stuff' or 'WIP' pollute the history, break changelog generation, and make it impossible to automate version bumps.

Enforce conventional commits with commitlint in CI:

# .github/workflows/lint-commits.yml
on:
  pull_request:
    types: [opened, synchronize, reopened, edited]

jobs:
  commitlint:
    runs-on: ubuntu-latest
    steps:
      - uses: actions/checkout@v4
        with:
          fetch-depth: 0
      - uses: actions/setup-node@v4
        with:
          node-version: '20'
      - run: npm install --no-save @commitlint/cli @commitlint/config-conventional
      - run: |
          npx commitlint \
            --from ${{ github.event.pull_request.base.sha }} \
            --to ${{ github.event.pull_request.head.sha }} \
            --verbose

commitlint.config.js:

module.exports = { extends: ['@commitlint/config-conventional'] };

Blocking the PR until all commits pass commitlint enforces the convention at the point of code review, not after the fact. fetch-depth: 0 is required so commitlint can access all commits in the PR range.