Run docker build only once and also on tag

.github/workflows/main.yml

@@ -3,7 +3,7 @@ name: Run tests & Publish to Docker Registry
 on: [push, pull_request]
 
 jobs:
-  build:
+  test:
     runs-on: ubuntu-latest
     strategy:
       max-parallel: 4
@@ -93,8 +93,13 @@ jobs:
           name: code-coverage-report
           path: htmlcov
 
+  build:
+    runs-on: ubuntu-latest
+    needs: ['test']
+
+    steps:
       - name: Publish to Docker Registry
-        if: github.event_name == 'push' && github.ref == 'refs/heads/master'
+        if: github.event_name == 'push' && (github.ref == 'refs/heads/master' || startsWith(github.ref, 'refs/tags/v'))
         uses: docker/build-push-action@v1
         with:
           repository: simplelogin/app-ci
@@ -103,7 +108,7 @@ jobs:
           tag_with_ref: true
 
       - name: Create Sentry release
-        if: github.event_name == 'push' && github.ref == 'refs/heads/master'
+        if: github.event_name == 'push' && (github.ref == 'refs/heads/master' || startsWith(github.ref, 'refs/tags/v'))
         uses: getsentry/action-release@v1
         env:
           SENTRY_AUTH_TOKEN: ${{ secrets.SENTRY_AUTH_TOKEN }}