ci: run only the "build tagged container image" step on tag pushes

.github/workflows/build-container.yml

@@ -1,4 +1,4 @@
-name: Update Docker image
+name: Build container image
 
 on:
   push:
@@ -12,6 +12,7 @@ jobs:
     if: github.repository_owner == 'gbdev'
     runs-on: ubuntu-latest
     permissions:
+      # So that the workflow can write to the ghcr an upload there
       packages: write
     steps:
       - name: Checkout repo
@@ -25,16 +26,19 @@ jobs:
           password: ${{ secrets.GITHUB_TOKEN }}
         
       - name: Build and push the master container image
+        # When a commit is pushed to master
+        if: github.ref == 'refs/heads/master'
         run: |
           COMMIT_HASH=$(git rev-parse --short HEAD)
           sed -i "2i LABEL org.opencontainers.image.description=\"RGBDS container image, containing the git version master:$COMMIT_HASH\"" Dockerfile
           docker build . --tag ghcr.io/gbdev/rgbds:master
           docker push ghcr.io/gbdev/rgbds:master
         
-      - name: Tag release container image
+      - name: Build and push the version-tagged container image
+        # When a tag is pushed
         if: startsWith(github.ref, 'refs/tags/')
         run: |
           TAG_NAME=${GITHUB_REF#refs/tags/}
-          sed -i "2i LABEL org.opencontainers.image.description=\"RGBDS container image for version $TAG_NAME\"" Dockerfile
+          sed -i "2i LABEL org.opencontainers.image.description=\"RGBDS container image for the release version $TAG_NAME\"" Dockerfile
           docker build . --tag ghcr.io/gbdev/rgbds:$TAG_NAME
           docker push ghcr.io/gbdev/rgbds:$TAG_NAME