PR title or custom commit validation on GitHub Action

[SiegeSailor]

Use Case

Allow the GitHub Action to input the PR title or a custom text field for Conventional Commit style validation.

Proposed Solution

With a Boolean PR title validation:

- name: Action | Validate Commit Messages
        uses: opensource-nepal/commitlint@v1
        with:
            # Set to true to validate the PR title. Default to true.
            # This setting should be ignored when it is not a PR or when github.event.pull_request.title is empty
            pull-request-title: true

Or, with a custom text validation (this might be particularly useful in actions):

- name: Action | Validate Commit Messages
        uses: opensource-nepal/commitlint@v1
        with:
            # Only validate this commit if the value is not empty
            commit: ""

Alternative Considered

I installed commitlint on my runner (see https://github.com/SiegeSailor/Smarty-Notebook/actions/runs/19213985568/job/54920491842 for details):

jobs:
  linting:
    runs-on: ubuntu-latest

    permissions:
      contents: read
      pull-requests: read

    steps:
      - name: Action | Checkout Repository on Pull Request
        uses: actions/checkout@v5
        if: github.event_name == 'pull_request'
        with:
          fetch-depth: 1
          ref: ${{ github.event.pull_request.head.sha }}
          token: ${{ secrets.GITHUB_TOKEN }}

      - name: Action | Set Up Python
        uses: actions/setup-python@v6
        if: github.event_name == 'pull_request'
        with:
          python-version: "3.11.13"

      - name: Setup | Install Commitlint
        if: github.event_name == 'pull_request'
        run: |
          pip install commitlint

      - name: Evaluate | Validate PR Title
        if: github.event_name == 'pull_request'
        run: |
          commitlint "${{ github.event.pull_request.title }}"

When it is not a PR:

By the way, the following doesn't work. The GitHub Action commitlint seems not to read the local commits on the runner (see https://github.com/SiegeSailor/Smarty-Notebook/actions/runs/19212728519/job/54917412427):

steps:
  - name: Action | Checkout Repository on Pull Request
    uses: actions/checkout@v5
    if: github.event_name == 'pull_request'
    with:
      fetch-depth: 0
      ref: ${{ github.event.pull_request.head.sha }}
      token: ${{ secrets.GITHUB_TOKEN }}

  - name: Setup | Commit PR Title
    if: github.event_name == 'pull_request'
    run: |
      git config user.name "github-actions[bot]"
      git config user.email "41898282+github-actions[bot]@users.noreply.github.com"
      git commit --allow-empty -m "${{ github.event.pull_request.title }}"

  - name: Action | Validate Commit Messages
    uses: opensource-nepal/commitlint@v1

  - name: Cleanup | Revert PR Title Commit
    if: github.event_name == 'pull_request'
    run: |
      git reset --hard HEAD~1

Additional context

Another GitHub Action CashStory/commitizen-action-pr seems to be a particular fit, but it comes with some issues (see CashStory/commitizen-action-pr#2) and is not in an active status.