ci: Use official Docker GitHub Action for publication to Docker Hub (#…

…808)

* Use official Docker GitHub Action to publish to Docker Hub
   - Tag image with version release and 'latest-stable' tags if the push is a tag release

.github/workflows/publish-docker.yml

@@ -0,0 +1,35 @@
+name: Publish Docker Images
+
+on:
+  push:
+    branches:
+    - master
+    tags:
+    - v*
+
+jobs:
+  build-and-publish:
+    name: Build and publish Docker images to Docker Hub
+    runs-on: ubuntu-latest
+
+    steps:
+    - uses: actions/checkout@master
+    - name: Build and Publish to Registry
+      if: "! ${{ startsWith(github.ref, 'refs/tags/') }}"
+      uses: docker/build-push-action@v1
+      with:
+        username: ${{ secrets.DOCKER_USERNAME }}
+        password: ${{ secrets.DOCKER_PASSWORD }}
+        repository: pyhf/pyhf
+        dockerfile: docker/Dockerfile
+        tags: latest
+    - name: Build and Publish to Registry with Release Tag
+      if: ${{ startsWith(github.ref, 'refs/tags/') }}
+      uses: docker/build-push-action@v1
+      with:
+        username: ${{ secrets.DOCKER_USERNAME }}
+        password: ${{ secrets.DOCKER_PASSWORD }}
+        repository: pyhf/pyhf
+        dockerfile: docker/Dockerfile
+        tags: latest,latest-stable
+        tag_with_ref: true