Today, I learned that creating a pull request with GitHub Actions won't trigger on: pull_request workflows by default. According to Github doc, this behavior is intentional to prevent recursive workflow runs.

To solve the issue, this repo list all possible solutions. Personally, I prefer to use the Github App token approach as it's more secure.

Here's how you can set up the Github App token:

1. Follow this step to create a Github App token with the necessary permissions.
2. Add the Github App token to the workflow file.

Since I use Github CLI, I configured it as below:

steps:
  # Generate the Github App token
  # based on given app-id and private-key
  - uses: actions/create-github-app-token@v1
    id: generate-token
    with:
      app-id: ${{ secrets.APP_ID }}
      private-key: ${{ secrets.APP_PRIVATE_KEY }}

  - name: Create backport PR
    # Use the Github App token
    env:
      GITHUB_TOKEN: ${{ steps.generate-token.outputs.token }}
    # Create a pull request with the Github CLI
    run: |
      gh pr create \
        --base main \
        --head $BACKPORT_BRANCH \

After using Github App token, the on: pull_request can be triggered as seen below.