fast_forward.yml

name: Fast-forward and Parse Changelog
# Triggered by "/fast-forward" comment in PR.
# Copied from https://github.com/khanshoaib3/stardew-access/blob/development/.github/workflows/fast-forward.yml
on:
  issue_comment:
    types: [ created, edited ]

jobs:
  fast_forward:
    name: fast-forward

    runs-on: ubuntu-latest

    # Only run the job if:-
    # 1. It is a pull request
    # 2. It's not closed
    # 3. The comment was by the owner or one of the collaborator
    # 4. The comment message is "/fast-forward"
    if: |
      github.event.issue.pull_request &&
      !github.event.issue.closed_at &&
      github.event.issue.state == 'open' &&
      (github.event.comment.author_association == 'OWNER' || github.event.comment.author_association == 'COLLABORATOR') && 
      contains(github.event.comment.body, '/fast-forward')

    steps:
      - name: Fetch repository
        uses: actions/checkout@v4
        with:
          fetch-depth: 0
          token: ${{ secrets.GH_TOKEN }}

      # API: https://docs.github.com/en/rest/pulls/pulls?apiVersion=2022-11-28#get-a-pull-request
      - name: Get PR details
        uses: octokit/request-action@v2.x
        id: get-pr-details
        with:
          route: GET /repos/{repository}/pulls/{pull_number}
          repository: ${{ github.repository }}
          pull_number: ${{ github.event.issue.number }}
        env:
          GITHUB_TOKEN: ${{ secrets.GH_TOKEN }}

      - name: Set environment variables
        run: |
          MERGE_STATUS=${{ fromJson(steps.get-pr-details.outputs.data).mergeable }}
          if $MERGE_STATUS; then echo "COMMENT=\[Fast Forward CI\] ${{ env.HEAD_REF }} cannot be merged into ${{ env.BASE_REF }} at the moment." >> $GITHUB_ENV; fi
          echo "MERGE_STATUS=$MERGE_STATUS" >> $GITHUB_ENV
          echo "BASE_REF=${{ fromJson(steps.get-pr-details.outputs.data).base.ref }}" >> $GITHUB_ENV
          echo "HEAD_REF=${{ fromJson(steps.get-pr-details.outputs.data).head.ref }}" >> $GITHUB_ENV

      # Merges the head branch into base branch
      # Only runs if the merge status is "clean", clean might refer to when the merge button is green in the PR's page, there's no clear indication of it's values in docs
      # For forks the following script adds the fork as a remote, them merges it into base
      - name: Merge the head branch into base in a fast forward manner only
        if: ${{ env.MERGE_STATUS }}
        run: |
          git config --global user.email "action@github.com"
          git config --global user.name "GitHub Action"
          git checkout ${{ env.BASE_REF }}
          git pull origin ${{ env.BASE_REF }}
          if ${{ fromJson(steps.get-pr-details.outputs.data).head.repo.fork }}; then
            USER_NAME=${{ fromJson(steps.get-pr-details.outputs.data).head.user.login }}
            git remote add $USER_NAME ${{ fromJson(steps.get-pr-details.outputs.data).head.repo.clone_url }}
            git pull $USER_NAME ${{ env.HEAD_REF }}
            git merge --ff-only $USER_NAME/${{ env.HEAD_REF }}
          else
            git pull origin ${{ env.HEAD_REF }}
            git merge --ff-only origin/${{ env.HEAD_REF }}
          fi
          echo "COMMENT=\[Fast Forward CI\] ${{ env.HEAD_REF }} merged into ${{ env.BASE_REF }}..." >> $GITHUB_ENV

      # Executes the python script to copy the changelog from the PR's body to docs/changelogs/latest.md file
      # It also saves the response into response.txt at the repo's base
      # Cuts the lines before "## Changelog" line in the PR's body using the "sed" command
      # Ref: https://stackoverflow.com/a/35966027
      - name: Copy the changelogs from pr message to latest.md
        if: ${{ env.MERGE_STATUS }}
        run: |
          cd ./docs/changelogs
          echo "$ISSUE_BODY" > pr_msg.txt
          python copy_changelogs_to.py pr_msg.txt latest.md > ../../response.txt
          cat ../../response.txt
          cd ../../
        env:
          ISSUE_BODY: ${{ github.event.issue.body }}

      # Commit the changes if there was no error i.e., there was no issue in fetching the files and there was actually a changelog found/copied
      - name: Commit the changes (if any)
        if: ${{ env.MERGE_STATUS }}
        run: |
          if [[ "$( tail ./response.txt -n 1 )" == 'No changes to write!' ]] || [[ "$( tail ./response.txt -n 1 )" =~ "File \`(.*?)\` not found\!" ]]; then
            echo "COMMENT=${{ env.COMMENT }}\nNo changelogs found..." >> $GITHUB_ENV
          else
            git add docs/changelogs/latest.md
            git commit -m "chore(ff ci): add changelogs from #${{ github.event.issue.number }} to docs/changelog/latest.md"
            echo "COMMENT=${{ env.COMMENT }} Copied the changelogs from pull request body to docs/changelog/latest.md..." >> $GITHUB_ENV
          fi

      - name: Push to origin
        if: ${{ env.MERGE_STATUS }}
        run: |
          git push origin
          echo "COMMENT=${{ env.COMMENT }} Pushed the changes to origin." >> $GITHUB_ENV

      # Post a success/failure comment to the PR.
      - name: Add success/failure comment to PR
        uses: octokit/request-action@v2.x
        with:
          route: POST /repos/{repository}/issues/{issue_number}/comments
          repository: ${{ github.repository }}
          issue_number: ${{ github.event.issue.number }}
          body: ${{ env.COMMENT }}
        env:
          GITHUB_TOKEN: ${{ secrets.GH_TOKEN }}

      # Post a failure message when any of the previous steps fail.
      - name: Add failure comment to PR
        if: ${{ failure() }}
        uses: octokit/request-action@v2.x
        with:
          route: POST /repos/{repository}/issues/{issue_number}/comments
          repository: ${{ github.repository }}
          issue_number: ${{ github.event.issue.number }}
          body: \[Fast Forward CI\] PR cannot be merged in. Check the Actions tab for details.
        env:
          GITHUB_TOKEN: ${{ secrets.GH_TOKEN }}