do not rebuild for readme-only changes

.github/workflows/build-docker.yaml

@@ -2,29 +2,53 @@ name: Build and Push Docker Image
 
 on:
   push:
-    branches: 
-      - main  # or any other branch you want to trigger on
+    branches:
+      - main
 
 jobs:
-  build-and-push:
+  ignore-readme-only-changes:
     runs-on: ubuntu-latest
-
+    outputs:
+      run_build: ${{ steps.filter.outputs.run_build }}
     steps:
-    - name: Check out the repo
-      uses: actions/checkout@v2
-
-    - name: Set up Docker Buildx
-      uses: docker/setup-buildx-action@v1
-
-    - name: Log in to Docker Hub
-      uses: docker/login-action@v1
-      with:
-        username: builder555
-        password: ${{ secrets.DOCKER_HUB_ACCESS_TOKEN }}
+      - name: Check out the repo
+        uses: actions/checkout@v2
+      - id: filter
+        name: Check if README.md was updated
+        run: |
+          if git diff --name-only ${{ github.event.before }} ${{ github.sha }} | grep -iqvE '^(readme.md)$'
+          then
+            echo "::set-output name=run_build::true"
+          else
+            echo "::set-output name=run_build::false"
+          fi
 
-    - name: Build and push multi-platform Docker image
-      uses: docker/build-push-action@v2
-      with:
-        push: true
-        tags: builder555/pricewatch:latest
-        platforms: linux/amd64,linux/arm64,linux/arm/v7
+  build-and-push:
+    needs: ignore-readme-changes
+    if: needs.check-modified-files.outputs.run_build == 'true'
+    runs-on: ubuntu-latest
+    steps:
+      - name: Check out the repo
+        uses: actions/checkout@v2
+      - name: Check for README.md changes
+        id: readme_check
+        run: |
+          if git diff --name-only ${{ github.event.before }} ${{ github.sha }} | grep -v 'README.md'
+          then
+            echo "README_CHANGE=false" >> $GITHUB_ENV
+          else
+            echo "README_CHANGE=true" >> $GITHUB_ENV
+          fi
+      - name: Set up Docker Buildx
+        uses: docker/setup-buildx-action@v1
+      - name: Log in to Docker Hub
+        uses: docker/login-action@v1
+        with:
+          username: builder555
+          password: ${{ secrets.DOCKER_HUB_ACCESS_TOKEN }}
+      - name: Build and push multi-platform Docker image
+        uses: docker/build-push-action@v2
+        with:
+          push: true
+          tags: builder555/pricewatch:latest
+          platforms: linux/amd64,linux/arm64,linux/arm/v7