Adjusted Makefile to operate with nix

Also, loading + extracting image ID in one line.

Ref: docker/cli#2212 (comment)

.github/workflows/publish-docker-image-to-github-registry.yml

@@ -24,7 +24,7 @@ jobs:
 
       - name: Push docker image to ghcr.io
         run: |
-          IMG_ID=$( docker images --filter "reference=oci-srm-server-mock-rust" --format "{{.ID}}" )
+          IMG_ID=$$(docker load -i result | sed -nr 's/^Loaded image: (.*)$/\1/p' | xargs -I{} docker image ls "{}" --format="{{.ID}}")
           echo "Tagging $IMG_ID"
           docker tag $IMG_ID ghcr.io/ocramius/oci-srm-server-mock-rust:${{ github.event.release.tag_name }}
           docker push ghcr.io/ocramius/oci-srm-server-mock-rust:${{ github.event.release.tag_name }}

Makefile

@@ -5,10 +5,12 @@ run:
 	PUNCHOUT_SERVER_CONFIRMATION_URI=http://localhost:1111/ \
 	OCI_SRM_SERVER_MOCK_BASE_URL=http://localhost:8089/ \
 	OCI_SRM_SERVER_MOCK_PORT=8089 \
-	 cargo run
+	 nix run
 
-buildx:
-	docker buildx build -t oci-srm-server-mock:latest --load .
+build:
+	nix build .\#docker-image
+	IMG_ID=$$(docker load -i result | sed -nr 's/^Loaded image: (.*)$/\1/p' | xargs -I{} docker image ls "{}" --format="{{.ID}}")
+	docker tag $$IMG_ID ci-srm-server-mock:latest
 
 docker:
 	docker run \