Fix CI build failure and tag creation issues in release workflow

- Add fetch-tags: true to ensure git tags are available during checkout
- Improve tag existence checking with proper git rev-parse verification
- Add pre-check to prevent attempting to create tags that already exist
- Fix tag creation logic to handle existing tags gracefully

Resolves both the 'git rev-list' exit code 129 error and the 'Reference
already exists' error in the release workflow.

Author: antonym

.github/workflows/release.yml

@@ -74,7 +74,11 @@ jobs:
         IMAGE_RELEASE=$(echo ${IMAGE_INFO} | jq -r '.Labels.build_version' | awk '{print $3}')
         IMAGE_VERSION=$(echo ${IMAGE_RELEASE} | awk -F'-nbxyz' '{print $1}')
         NB_RELEASE_NUMBER=$(echo ${IMAGE_RELEASE} | awk -F'-nbxyz' '{print $2}')
-        TAG_SHA=$(git rev-list -n 1 ${IMAGE_RELEASE} 2>/dev/null || echo "")
+        if git rev-parse --verify "refs/tags/${IMAGE_RELEASE}" >/dev/null 2>&1; then
+          TAG_SHA=$(git rev-list -n 1 ${IMAGE_RELEASE})
+        else
+          TAG_SHA=""
+        fi
         if [ -z "${MULTIDIGEST}" ] || [ "${MULTIDIGEST}" == "null" ]; then
           echo "**** No existing container build found, assuming first build ****"
           VERSION_TAG=${WEBAPP_RELEASE}-nbxyz1
@@ -138,8 +142,20 @@ jobs:
           ghcr.io/netbootxyz/netbootxyz:${{ env.VERSION_TAG }}
         labels: ${{ steps.meta.outputs.labels }}
 
-    - name: Bump version and push tag
+    - name: Check if tag exists
       if: steps.version_check.outcome == 'success' && steps.version_check.conclusion == 'success'
+      id: check_tag
+      run: |
+        if git rev-parse --verify "refs/tags/${{ env.VERSION_TAG }}" >/dev/null 2>&1; then
+          echo "Tag ${{ env.VERSION_TAG }} already exists, skipping tag creation"
+          echo "tag_exists=true" >> $GITHUB_OUTPUT
+        else
+          echo "Tag ${{ env.VERSION_TAG }} does not exist, will create"
+          echo "tag_exists=false" >> $GITHUB_OUTPUT
+        fi
+
+    - name: Bump version and push tag
+      if: steps.version_check.outcome == 'success' && steps.version_check.conclusion == 'success' && steps.check_tag.outputs.tag_exists == 'false'
       id: tag_version
       uses: anothrNick/[email protected]
       env: