Manual GitHub Action for creating a release and publishing release details to Slack

release.yml

# This github action is a Manual workflow that will create a release and generate release notes from
# merged pull requests.  After creating the release, it will generate a Slack message from the release
# notes and publish a release notification to a given Slack channel.
#
# Relevant links:
# - https://docs.github.com/en/actions/managing-workflow-runs/manually-running-a-workflow
# - https://app.slack.com/block-kit-builder
#
# This file goes into your project's .github/workflows folder

name: Create release

# Can change this to "push" during testing
on: workflow_dispatch

jobs:
  create-release:
    runs-on: ubuntu-latest
    steps:
      # version number generation can be changed to whatever you like, uses the current time to ensure uniqueness during testing
      - name: Assign version
        run: |
          version="$(date +"%Y.%m.%d.%s")"
          echo "Using version $version"
          echo "RELEASE_VERSION=$version" >> $GITHUB_ENV

      - name: Release
        id: release
        uses: softprops/action-gh-release@v1
        with:
          tag_name: ${{ env.RELEASE_VERSION }}
          generate_release_notes: true

      - uses: octokit/request-action@v2.1.6
        id: get_latest_release
        with:
          route: GET /repos/${{ github.repository }}/releases/tags/${{ env.RELEASE_VERSION }}
        env:
          GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}

      - uses: devops-actions/json-to-file@v1.0.0
        with:
          json: "${{ fromJson(steps.get_latest_release.outputs.data).body }}"
          filename: RELEASE_NOTES

      - name: Release notes formatting - Strip html comment from the beginning of release notes
        run: sed --in-place -e 's/<\!--[^>]*-->//g' RELEASE_NOTES && cat RELEASE_NOTES

      - name: Release notes formatting - Strip "full changelog" link
        run: sed --in-place -e 's/\*\*Full Changelog.*//g' RELEASE_NOTES && cat RELEASE_NOTES

      - name: Release notes formatting - Strip new contributor section
        run: |
          sed --in-place -E -e 's/## New Contributors.*//' RELEASE_NOTES
          sed --in-place -E -e 's/\* .+? made their first contribution .+?//' RELEASE_NOTES
          cat RELEASE_NOTES

      - name: Release notes formatting - Replace markdown bullets with a more slack-compatible format
        run: sed --in-place -E -e 's/\* (.+?) (by .+?) in (http.+?)/- <\3|\1> \2/' RELEASE_NOTES && cat RELEASE_NOTES

      - name: Release notes formatting - Replace headers with bold text
        run: sed --in-place -E -e 's/## (.*)/*\1*/' RELEASE_NOTES && cat RELEASE_NOTES

      - name: Ensure release body is JSON-friendly
        run: |
          jq --null-input '{"body": $releaseNotes}' --rawfile releaseNotes RELEASE_NOTES > RELEASE_NOTES_JSON && cat RELEASE_NOTES_JSON

      - name: Assign release notes to step variable
        id: release-notes-formatting
        run: echo "::set-output name=RELEASE_NOTES::$(cat RELEASE_NOTES_JSON | jq '.body')"

      - name: notify-slack
        id: slack
        uses: slackapi/slack-github-action@v1.21.0
        with:
          # Slack channel id, channel name, or user id to post message.
          # See also: https://api.slack.com/methods/chat.postMessage#channels
          channel-id: 'my-slack-channel'
          payload: |
            {
              "text": "",
              "blocks": [
                {
                  "type": "section",
                  "text": {
                    "type": "mrkdwn",
                    "text": "<${{ steps.release.outputs.url }}|v${{ env.RELEASE_VERSION }}> has been released."
                  }
                },
                {
                  "type": "section",
                  "text": {
                    "type": "mrkdwn",
                    "text": ${{ steps.release-notes-formatting.outputs.RELEASE_NOTES }}
                  }
                }
              ]
            }
        env:
          SLACK_WEBHOOK_URL: ${{ secrets.SLACK_WEBHOOK }}
          SLACK_WEBHOOK_TYPE: INCOMING_WEBHOOK

Here's an example of what this looks like: