Generate tag name sooner

For quicker failures.

Signed-off-by: Stephen Finucane <stephen@that.guru>
(cherry picked from commit 951253a)

Author: stephenfin

.github/workflows/publish-image.yaml

@@ -12,6 +12,14 @@ jobs:
     name: Push container image to GitHub Container Registry
     runs-on: ubuntu-latest
     steps:
+      - name: Generate tag name
+        run: |
+          if [[ ${BRANCH} == "main" ]]; then
+              IMAGE_TAG="latest"
+          else
+              IMAGE_TAG="${BRANCH/\//-}"
+          fi
+          echo "IMAGE_TAG=${IMAGE_TAG}" >> $GITHUB_ENV
       - name: Set up QEMU
         uses: docker/setup-qemu-action@v3
       - name: Set up Docker Buildx
@@ -22,14 +30,6 @@ jobs:
           registry: ghcr.io
           username: ${{ github.actor }}
           password: ${{ secrets.GITHUB_TOKEN }}
-      - name: Generate tag name
-        run: |
-          if [[ ${BRANCH} == "main" ]]; then
-              IMAGE_TAG="latest"
-          else
-              IMAGE_TAG="${BRANCH/\//-}"
-          fi
-          echo "IMAGE_TAG=${IMAGE_TAG}" >> $GITHUB_ENV
       - name: Build and push container image
         uses: docker/build-push-action@v6
         with: