Auto-tag whenever version in MODULE.bazel changes

.github/workflows/ci.yml

@@ -236,3 +236,42 @@ jobs:
         with:
           name: ${{ env.OUT }}
           path: ${{ env.OUT }}.tar.gz
+
+  release-tagging:
+    name: Version Tagging
+    runs-on: ubuntu-24.04
+    if: ${{github.event_name == 'push' && (github.ref == 'refs/heads/main' || github.ref == 'refs/heads/main')}}
+    permissions:
+      contents: write
+
+    steps:
+      - uses: actions/checkout@v2
+        with:
+          fetch-depth: 0
+          token: ${{ secrets.GITHUB_TOKEN }}
+
+      - name: Tag with MODULES.bazel version if not already.
+        run: |
+          version_from_module_bazel() {
+            git annotate -l MODULE.bazel \
+            | awk '/module/  { in_module=1; }
+                   /version/ { if (in_module) { print $0; nextfile; } }' \
+            | sed  's/\(^[0-9a-f]*\).*version[ ]*=[ ]*"\([0-9.]*\)".*/\1 \2/p;d'
+          }
+
+          git config --local user.name "Development Bot"
+          git config --local user.email bot@bant.build"
+
+          # We want to tag whenever the version in MODULE.bazel changes.
+          # So extract the hash of when the current version was entered.
+          read TAG_HASH TAG_VERSION <<<$(version_from_module_bazel)
+
+          echo "Bant Version v${TAG_VERSION} at hash ${TAG_HASH}"
+
+          # If this is the first time we see this tag: apply.
+          if [ -z "$(git tag -l "v${TAG_VERSION}")" ]; then
+            git tag -a "v${TAG_VERSION}" ${TAG_HASH} -m "Update to v${TAG_VERSION}"
+            git push origin "v${TAG_VERSION}"
+          else
+            echo "Tag already applied"
+          fi