Update test-docker-build.yml

.github/workflows/test-docker-build.yml

@@ -25,20 +25,22 @@ jobs:
       - name: Run step if only the files listed above change
         if: steps.changed-files.outputs.any_changed == 'true'
         id: set-matrix
-        env:
-          CHANGED_FILES: ${{ steps.changed-files.outputs.all_changed_files}}
         run: |
-          for file in ${CHANGED_FILES}; do
+          for file in ${{ steps.changed-files.outputs.all_changed_files}}; do
             echo "$file was changed"
           done 
-          echo ${CHANGED_FILES}
           echo ${{ steps.changed-files.outputs.all_changed_files}}
           echo "matrix=[\"${{ steps.changed-files.outputs.all_changed_files}}\"] |sed 's/ /\", \"/g'" >> $GITHUB_OUTPUT
   build_modified_files:
-    runs-on: ubuntu-latest
     needs: get_changed_files
     name: Build Docker images on modified files
+    runs-on: ubuntu-latest
+    strategy:
+      matrix:
+        docker-file: ${{ fromJSON(needs.get_changed_files.outputs.matrix) }} # https://docs.github.com/en/actions/learn-github-actions/expressions#example-returning-a-json-object
     steps:
-      - name: Print env variables
-        run: |
-          echo ${{ needs.get_changed_files.outputs.matrix }}
+      - name: Build Docker image
+        uses: docker/build-push-action@v4
+        with:
+          context: ${{ matrix.docker-file }}
+          push: False