fix: detect Docker image version for update checks

.github/workflows/docker-build.yml

@@ -26,6 +26,8 @@ jobs:
     steps:
       - name: Checkout
         uses: actions/checkout@v4
+        with:
+          fetch-depth: 0
 
       - name: Set up QEMU
         uses: docker/setup-qemu-action@v3
@@ -52,7 +54,18 @@ jobs:
             type=semver,pattern={{version}}
             type=semver,pattern={{major}}.{{minor}}
             type=sha,prefix=sha-
-            type=raw,value=latest,enable={{is_default_branch}}
+            type=raw,value=latest,enable=${{ github.event_name != 'pull_request' && (github.ref == 'refs/heads/main' || startsWith(github.ref, 'refs/tags/v')) }}
+
+      - name: Determine image version
+        id: version
+        shell: bash
+        run: |
+          if [[ "$GITHUB_REF" == refs/tags/v* ]]; then
+            version="$GITHUB_REF_NAME"
+          else
+            version="$(git describe --tags --abbrev=0 2>/dev/null || git rev-parse --short=12 HEAD)"
+          fi
+          echo "version=$version" >> "$GITHUB_OUTPUT"
 
       - name: Build and push Docker image
         uses: docker/build-push-action@v6
@@ -63,6 +76,6 @@ jobs:
           tags: ${{ steps.meta.outputs.tags }}
           labels: ${{ steps.meta.outputs.labels }}
           build-args: |
-            VERSION=${{ startsWith(github.ref, 'refs/tags/v') && github.ref_name || '' }}
+            VERSION=${{ steps.version.outputs.version }}
           cache-from: type=gha
           cache-to: type=gha,mode=max