Add workflow to automatically update the bundle

.github/workflows/update-bundle.yml

@@ -0,0 +1,82 @@
+name: Update default CodeQL bundle
+
+on:
+  release:
+    types: [prereleased]
+
+jobs:
+  update-bundle:
+    if: startsWith(github.event.release.tag_name, 'codeql-bundle-')
+    runs-on: ubuntu-latest
+    steps:
+      - name: Dump environment
+        run: env
+
+      - name: Dump GitHub context
+        env:
+          GITHUB_CONTEXT: '${{ toJson(github) }}'
+        run: echo "${GITHUB_CONTEXT}"
+
+      - uses: actions/checkout@v3
+
+      - name: Update git config
+        run: |
+          git config --global user.email "github-actions@github.com"
+          git config --global user.name "github-actions[bot]"
+
+      - name: Update bundle
+        uses: ./.github/actions/update-bundle
+
+      - name: Rebuild Action
+        run: npm run build
+
+      - name: Commit and push changes
+        env:
+          RELEASE_TAG: "${{ github.event.release.tag_name }}"
+        run: |
+          git checkout -b "update-bundle/${RELEASE_TAG}"
+          git commit -am "Update default bundle to ${RELEASE_TAG}"
+          git push --set-upstream origin "update-bundle/${RELEASE_TAG}"
+
+      - name: Open pull request
+        env:
+          GH_TOKEN: ${{ secrets.GITHUB_TOKEN }}
+        run: |
+          cli_version=$(jq -r '.cliVersion' src/defaults.json)
+          pr_url=$(gh pr create \
+            --title "Update default bundle to $cli_version" \
+            --body "This pull request updates the default CodeQL bundle, as used with \`tools: latest\` and on GHES, to $cli_version." \
+            --assignee "${GITHUB_ACTOR}" \
+            --draft \
+          )
+          echo "CLI_VERSION=$cli_version" >> $GITHUB_ENV
+          echo "PR_URL=$pr_url" >> $GITHUB_ENV
+
+      - name: Create changelog note
+        shell: python
+        run: |
+          import os
+          import re
+
+          # Get the PR number from the PR URL.
+          pr_number = os.environ['PR_URL'].split('/')[-1]
+          changelog_note = f"- Update default CodeQL bundle version to {os.environ['CLI_VERSION']}. [#{pr_number}]({os.environ['PR_URL']})"
+
+          # If the "[UNRELEASED]" section starts with "no user facing changes", remove that line.
+          # Use perl to avoid having to escape the newline character.
+
+          with open('CHANGELOG.md', 'r') as f:
+              changelog = f.read()
+
+          changelog = changelog.replace('## [UNRELEASED]\n\nNo user facing changes.', '## [UNRELEASED]\n')
+
+          # Add the changelog note to the bottom of the "[UNRELEASED]" section.
+          changelog = re.sub(r'\n## (\d+\.\d+\.\d+)', f'{changelog_note}\n\n## \\1', changelog, count=1)
+
+          with open('CHANGELOG.md', 'w') as f:
+              f.write(changelog)
+
+      - name: Push changelog note
+        run: |
+          git commit -am "Add changelog note"
+          git push