Determine source branch name on merge push in GitHub action workflow

Question

I have a GitHub action workflow where I am doing a merge of various different source branches into target branch main.

Here is a test workflow to read the values of env variables:

name: Print Github Env Variables
on:
  push:
    branches:
      - main
      - test
  pull_request:
    branches:
      - main
      - test
  workflow_dispatch:
jobs:
  print-env-variabes:
    name: Print Github Variables
    runs-on: ubuntu-latest
    steps:
      - name: Print Github Variables
        run: |
          echo "GITHUB_WORKFLOW:$GITHUB_WORKFLOW"
          echo "GITHUB_EVENT_NAME:$GITHUB_EVENT_NAME"
          echo "GITHUB_EVENT_PATH:$GITHUB_EVENT_PATH"
          echo "GITHUB_WORKSPACE:$GITHUB_WORKSPACE"
          echo "GITHUB_SHA:$GITHUB_SHA"
          echo "GITHUB_REF:$GITHUB_REF"
          echo "GITHUB_HEAD_REF:$GITHUB_HEAD_REF"
      - name: Print complete webhook event payload
        run: cat $GITHUB_EVENT_PATH

Create test.txt file in a branch called test, create a pull request then merge into main. You will see what I am seeing then.

When I look at GITHUB_REF it contains main branch.

For pull_requests GITHUB_HEAD_REF contains ‘test’, but for push it is empty. I need the value when the files get merged, so when a push occurs.

The test workflow also prints out the entire event json object, on push event I didn’t see any entry with the branch ‘test’ in there either.

How do I get the name of the source branch during a push event?

Answer 1

This works for me after a merge request:

export LATESTLOG=$(git log -1 --pretty=%B)
export SOURCEBRANCH=$(echo $LATESTLOG | awk -F '\\\\n' '{print $1}' |  awk -F '/' '{print $2}' | awk '{print $1}')

Answer 2

name: Test closed branch

on:
  pull_request:
  types: [closed]

jobs:
  test:
    runs-on: ubuntu-latest
    steps:
      - uses: actions/checkout@v2
      - name: Get PR closed number
        env:
          PR_NUMBER: ${{ toJson(github.event.number) }}
        run: |
          echo "$PR_NUMBER"