fixup! Replace Travis CI with GitHub Actions

Author: lfdebrux

.github/workflows/publish.yaml

@@ -26,7 +26,21 @@ jobs:
         with:
           bundler-cache: true
 
+      - name: Check if new version to release
+        id: gem_version
+        run: |
+          gem_version=$(ruby -r rubygems -e "puts Gem::Specification::load('$(ls *.gemspec)').version")
+          echo "::set-output name=gem_version::$gem_version"
+
+          if git fetch origin "refs/tags/v$gem_version" >/dev/null 2>&1
+          then
+            echo "Tag 'v$gem_version' already exists"
+            echo "::set-output name=new_version::false"
+          else
+            echo "::set-output name=new_version::true"
+
       - name: Publish
+        if: ${{ steps.gem_version.outputs.new_version }}
         env:
           RUBYGEMS_API_KEY: ${{ secrets.RUBYGEMS_API_KEY }}
           GEM: govuk_tech_docs