Get the head ref branch name in GitHub Actions when PR is merged to main branch

I want to trigger a GitHub Actions workflow when a release/vX.Y.Z format of PR gets merged into the main branch.

I want the version number from this head branch i.e. "vX.Y.Z" so that I can create a release and tag it accordingly.

name: Auto PR Action

on:
  pull_request:
    branches: 
      - main
    types: [closed]
  

jobs:
  build:
    if: ${{ github.event.pull_request.merged }}
    runs-on: ubuntu-latest

    steps:
      - name: Extract version number
        run: |
          echo "${{ github.event.pull_request.base_ref }}"

          # Extract version number from the Release branch format: release/v1.2.3
          # E.g: release/v1.2.3 | sed 's/.*\///' will give us v1.2.3

          echo "${{ GET_THE_RELEASE_BRANCH_NAME }}" | sed 's/.*\///' >> $RELEASE_VERSION

      - name: Create Release
        id: create_release
        env:
          GH_TOKEN: ${{ github.token }}
        run: |
          gh release create $RELEASE_VERSION --generate-notes --latest --verify-tag

I always get the information about the base branch, i.e. main, but no info about the head branch.

How can we achieve this?

Solution

I want to trigger a GitHub Actions workflow when a release/vX.Y.Z format of PR gets merged into the main branch.

Here is something similar using the release-vX.Y.Z format:

on:
  pull_request:
    types:
      - closed

jobs:
  tag:
    if: contains(github.head_ref, 'release-') && contains(github.base_ref, 'main') && github.event.action == 'closed' && github.event.pull_request.merged == true
    runs-on: ubuntu-latest
    outputs:
      tag: ${{ steps.tag.outputs.tag }}
    steps:
      - name: Extract branch tag
        id: tag
        run: |
          BRANCH=${{ github.head_ref }}
          TAG="${BRANCH//release-/""}"
          echo $TAG
          echo "tag=$TAG" >> $GITHUB_OUTPUT

  release:
    needs:
      - TAG
    runs-on: ubuntu-latest
    env:
      TAG: ${{ needs.TAG.outputs.tag }}
    steps:
       [ ... ] # use $TAG to do something

This workflow will trigger when a PR is closed.

However, according to the if expression, the tag job will only be executed when the PR head branch use the release-vX.Y.Z format, and if the PR gets merged into the main branch.

Using this implementation, the tag variable and output will be equal to vX.Y.Z.