Add merge step

.github/workflows/validate.yml

@@ -1,10 +1,14 @@
+---
+# These jobs are run anytime a PR is opened against the main branch. In brief, to get a PR merged, you must:
+#   - Update the version number in pyproject.toml
+#   - Not have any linting issues (run `ruff format`)
+
 name: validate
 
 concurrency:
   group: validate
   cancel-in-progress: true
 
-#
 on:
   pull_request:
     branches:
@@ -74,16 +78,18 @@ jobs:
           src: './tb_pulumi'
           args: 'format --check'
 
-  # Cut a new branch if there isn't one with this version number
-  # cut-version-branch:
-  #   needs: detect-versions
-  #   runs-on: ubuntu-latest
-  #   permissions:
-  #     contents: write
-  #   if: needs.detect-versions.outputs.branch-exists == 'false'
-  #   steps:
-  #     - name: Create a new version branch
-  #       uses: peterjgrainger/[email protected]
-  #       with:
-  #         branch: ${{ needs.detect-versions.outputs.version }}
-  #         sha: ${{ github.event.pull_request.head.sha }}
+  # If the PR gets merged, cut a new version branch
+  merge:
+    needs: detect-versions
+    if: github.event.pull_request.merged == true && needs.detect-versions.outputs.branch-exists == 'false'
+    runs-on: ubuntu-latest
+    permissions:
+      contents: write
+    steps:
+      - uses: actions/checkout@v4
+
+      - name: Create a new version branch
+        uses: peterjgrainger/[email protected]
+        with:
+          branch: ${{ needs.detect-versions.outputs.version }}
+          sha: ${GITHUB_SHA}