name: Lint PR Title

# GitHub uses the pull request title as the commit subject when "Squash and
# merge" is used. When the repo is configured for squash-merge with the PR
# title as the commit title, individual commits on a PR branch are discarded
# by the squash, so this workflow — which validates the PR title against the
# Conventional Commits spec — is the sole enforcement point for the format of
# the commit that lands on main.

on:
  pull_request_target:
    types:
      - opened
      - edited
      - synchronize
      - reopened

permissions:
  pull-requests: read

jobs:
  lint:
    name: Validate PR Title
    runs-on: ubuntu-latest
    steps:
      - uses: amannn/action-semantic-pull-request@48f256284bd46cdaab1048c3721360e808335d50 # v6.1.1
        env:
          GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}
        with:
          # Conventional Commits types accepted by the commitizen commit-msg hook.
          types: |
            build
            chore
            ci
            docs
            feat
            fix
            perf
            refactor
            revert
            style
            test
          requireScope: false
          # Subject (text after the type/scope) must start lowercase.
          subjectPattern: ^(?![A-Z]).+$
          subjectPatternError: |
            The subject "{subject}" found in the pull request title "{title}"
            didn't match the configured pattern. Please ensure that the subject
            doesn't start with an uppercase character.