add docker multistage build

.github/workflows/docker.yml

@@ -0,0 +1,31 @@
+name: Docker
+
+on:
+  push:
+    branches:
+      - master
+      - main
+      - add-docker-build
+  pull_request:
+    branches:
+      - master
+      - main
+
+jobs:
+  build:
+    name: Build docker images
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v2
+
+      - name: build-test-image
+        run: docker build -f ./docker/Dockerfile -t modern-cpp-starter/greeter-test:1.0 --target test .
+
+      - name: build-app-image
+        run: docker build -f ./docker/Dockerfile -t modern-cpp-starter/greeter-app:1.0 .
+
+      - name: run-test-image
+        run: docker run modern-cpp-starter/greeter-test:1.0
+
+      - name: run-app-image
+        run: docker run modern-cpp-starter/greeter-app:1.0

docker/Dockerfile

@@ -0,0 +1,38 @@
+FROM ubuntu:20.04 as build
+# install dev tools
+ENV DEBIAN_FRONTEND=noninteractive
+RUN set -eux; \
+    apt-get update; \
+    apt-get install -y --no-install-recommends \
+    ca-certificates \
+    make \
+    cmake \
+    git \
+    gcc \
+    g++ \
+    ; \
+    rm -rf /var/lib/apt/lists/*
+# build in release mode
+WORKDIR /build-all
+COPY ./all ./all
+COPY ./cmake ./cmake
+COPY ./documentation ./documentation
+COPY ./include ./include
+COPY ./source ./source
+COPY ./standalone ./standalone
+COPY ./test ./test
+COPY ./CMakeLists.txt .
+RUN cmake -S all -B build -D CMAKE_BUILD_TYPE=Release
+RUN cmake --build build
+
+# make a test image - could also be done directly from/in the build image
+FROM ubuntu:20.04 as test
+WORKDIR /test
+COPY --from=build /build-all/build/test/GreeterTests ./
+CMD ["./GreeterTests"]
+
+# make an image to deploy our 'app'
+FROM ubuntu:20.04 as deploy
+WORKDIR /app
+COPY --from=build /build-all/build/standalone/Greeter ./
+CMD ["./Greeter"]