Update CI to do automatic tagging from version found in Makefile Issues: #489 Signed-off-by: Henner Zeller <hzeller@google.com>

diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index 1ab44d1..8242d83 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml

@@ -78,3 +78,35 @@
       env:
         OS: ${{ runner.os }}
         PLUGIN_NAME: ${{ matrix.plugin }}
+
+  release-tagging:
+    name: Version Tagging
+    runs-on: ubuntu-20.04
+    if: ${{github.event_name == 'push' && github.ref == 'refs/heads/main'}}
+    permissions:
+      contents: write
+
+    steps:
+    - uses: actions/checkout@v2
+      with:
+       fetch-depth: 0
+       token: ${{ secrets.GITHUB_TOKEN }}
+
+    - name: Tag with Makefile version if not already.
+      run: |
+        git config --local user.name "Development Bot"
+        git config --local user.email f4pga-dev@chipsalliance.org"
+
+        # We want to tag whenever the version in the Makefile changes.
+        # So extract the hash of when the current version was entered.
+        read TAG_HASH TAG_VERSION <<<$(git annotate -l Makefile | sed 's/\(^[0-9A-Fa-f]\+\).*PLUGIN_VERSION\s\+=\s\+\([0-9]\+\.[0-9]\+\).*/\1 \2/p;d')
+
+        echo "F4PGA Yosys Plugin 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