release.yml

name: Release

on:
  pull_request:
    branches: [ master ]
    types: [ closed ]

jobs:
  release:
    if: github.event.pull_request.merged == true && startsWith(github.event.pull_request.head.ref, 'release/')
    runs-on: ubuntu-latest

    steps:
      - uses: actions/checkout@v2
      
      - name: Setup variables
        id: setup
        run: |
          VERSION=$(echo ${{github.event.pull_request.head.ref}} | cut -d/ -f2)
          CHANGELOG=$(sed '0,/^## /d;/^## /Q' CHANGELOG.md)
          newline=$'\n'
          CHANGELOG="## v${VERSION}${newline}${CHANGELOG}"
          echo "::set-output name=version::$VERSION"
          echo "CHANGELOG<<EOF" >> $GITHUB_ENV
          echo "$CHANGELOG" >> $GITHUB_ENV
          echo "EOF" >> $GITHUB_ENV

      - name: Github Tag & Release
        uses: ncipollo/release-action@v1
        with:
          tag: "v${{ steps.setup.outputs.version }}"
          commit: ${{ github.event.pull_request.merge_commit_sha }}
          body: ${{ env.CHANGELOG }}
          token: ${{ secrets.GITHUB_TOKEN }}