結論

name: Release Drafter

on:
  push:
    branches:
      - stage

permissions:
  contents: read

jobs:
  update_release_draft:
    permissions:
      contents: write
      pull-requests: write
    runs-on: ubuntu-latest
    steps:
      - uses: actions/checkout@v4
      - name: setup bundleVersion
        run: |
          BUNDLE_VERSION=$(cat Unityのプロジェクト名/ProjectSettings/ProjectSettings.asset | grep bundleVersion: | tr -d "bundleVersion: ")
          echo $BUNDLE_VERSION
          echo "BUNDLE_VERSION=$BUNDLE_VERSION" >> $GITHUB_ENV
      - uses: release-drafter/release-drafter@v5
        with:
          name: ${{ env.BUNDLE_VERSION }}
          tag: ${{ env.BUNDLE_VERSION }}
          version: ${{ env.BUNDLE_VERSION }}
        env:
          GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}

何をやっているか

    steps:
      - uses: actions/checkout@v4

プロジェクト情報を得るため、チェックアウトする

      - name: setup bundleVersion
        run: |
          BUNDLE_VERSION=$(cat Unityのプロジェクト名/ProjectSettings/ProjectSettings.asset | grep bundleVersion: | tr -d "bundleVersion: ")
          echo $BUNDLE_VERSION
          echo "BUNDLE_VERSION=$BUNDLE_VERSION" >> $GITHUB_ENV

ProjectSettingsからbundleVersionを引っこ抜く

      - uses: release-drafter/release-drafter@v5
        with:
          name: ${{ env.BUNDLE_VERSION }}
          tag: ${{ env.BUNDLE_VERSION }}
          version: ${{ env.BUNDLE_VERSION }}

release-drafterのAction Inputsを用いて、BUNDLE_VERSIONを流し込む

生成例

UnityのbundleVersionをタイトルに、リリースノート作ってくれる