Fix github release action (#716)

* Fix build args parameter

* Only trigger when release published

* Get tag name from GITHUB_REF

.github/workflows/build.yml

@@ -3,19 +3,23 @@ name: Build
 
 on:
   release:
-    types: [published, created, edited]
+    types: [published]
 
 jobs:
   docker-image:
     runs-on: ubuntu-latest
     steps:
       - uses: actions/checkout@v2
 
+      - name: Extract tag name
+        id: vars
+        run: echo ::set-output name=tag::${GITHUB_REF#refs/*/}
+
       - name: Build and publish docker image
         uses: docker/build-push-action@v1.1.1
         with:
           repository: faforever/faf-python-server
           username: ${{ secrets.DOCKER_USERNAME }}
           password: ${{ secrets.DOCKER_PASSWORD }}
-          build-args: GITHUB_REF=${GITHUB_REF}
+          build_args: GITHUB_REF=${{ steps.vars.outputs.tag }}
           tag_with_ref: true