Update GitHub Actions workflow to compute and use a lowercase image name for Docker tags, ensuring consistency in image naming.

Author: tacxou

.github/workflows/tests-main.yml

@@ -28,6 +28,10 @@ jobs:
       - name: Checkout repository
         uses: actions/checkout@v4
 
+      - name: Compute lowercase image name
+        id: image_name
+        run: echo "value=ghcr.io/${GITHUB_REPOSITORY,,}:unstable" >> "$GITHUB_OUTPUT"
+
       - name: Log in to GitHub Container Registry
         uses: docker/login-action@v3
         with:
@@ -40,4 +44,4 @@ jobs:
         with:
           context: .
           push: true
-          tags: ghcr.io/${{ github.repository }}:unstable
+          tags: ${{ steps.image_name.outputs.value }}