[GHA] Only rebuild image if Dockerfile changed

Author: Quasar6X

.github/workflows/build.yaml

@@ -26,23 +26,39 @@ jobs:
       id-token: write
 
     steps:
+      - name: Checkout
+        uses: actions/checkout@v4
+
+      - name: Check for Docker changes
+        id: changes
+        run: |
+          if git diff --name-only ${{ github.event.before }} ${{ github.sha }} | grep '^\.devcontainer/Dockerfile'; then
+            echo "changed=true" >> $GITHUB_OUTPUT
+          else
+            echo "changed=false" >> $GITHUB_OUTPUT
+          fi
+
       - name: Log in to Container registry
+        if: ${{ steps.changes.outputs.changed == 'true' }}
         uses: docker/login-action@v3
         with:
           registry: ${{ env.REGISTRY }}
           username: ${{ github.actor }}
           password: ${{ secrets.GITHUB_TOKEN }}
 
       - name: Extract metadata for Docker
+        if: ${{ steps.changes.outputs.changed == 'true' }}
         id: meta
         uses: docker/metadata-action@v5
         with:
           images: ${{ env.REGISTRY }}/${{ env.IMAGE_NAME }}
 
       - name: Set up Docker Buildx
+        if: ${{ steps.changes.outputs.changed == 'true' }}
         uses: docker/setup-buildx-action@v3
 
       - name: Build Docker image
+        if: ${{ steps.changes.outputs.changed == 'true' }}
         id: push
         uses: docker/build-push-action@v6
         with:
@@ -54,6 +70,7 @@ jobs:
           cache-to: type=gha,mode=max
 
       - name: Generate artifact attestation
+        if: ${{ steps.changes.outputs.changed == 'true' }}
         uses: actions/attest-build-provenance@v3
         with:
           subject-name: ${{ env.REGISTRY }}/${{ env.IMAGE_NAME }}