Add GitHub Action workflow to build and publish to the GitHub Container registry

.github/workflows/docker.yml

@@ -0,0 +1,51 @@
+name: Publish Oxigraph server image
+
+on:
+  workflow_dispatch:
+  push:
+    # Publish `master` branch as Docker `latest` image.
+    branches:
+      - master
+    paths:
+    - 'Dockerfile'
+    - 'lib/**'
+    - 'server/**'
+    - '.github/workflows/docker.yml'
+  # Publish `v0.1.2` release as image tag `0.1.2`.
+  release:
+    types: [published]
+
+jobs:
+  build-and-publish:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v2
+
+      - name: Login to GitHub Container Registry
+        uses: docker/login-action@v1
+        with:
+          registry: ghcr.io
+          username: ${{github.actor}}
+          password: ${{secrets.GITHUB_TOKEN}}
+
+      - name: Generate image ID and version
+        run: |
+          IMAGE_ID=ghcr.io/${{ github.repository_owner }}/oxigraph
+          # Change all uppercase to lowercase
+          IMAGE_ID=$(echo $IMAGE_ID | tr '[A-Z]' '[a-z]')
+          # Strip git ref prefix from version
+          VERSION=$(echo "${{ github.ref }}" | sed -e 's,.*/\(.*\),\1,')
+          # Strip "v" prefix from tag name
+          [[ "${{ github.ref }}" == "refs/tags/"* ]] && VERSION=$(echo $VERSION | sed -e 's/^v//')
+          # Use Docker `latest` tag convention
+          [ "$VERSION" == "master" ] && VERSION=latest
+          echo "IMAGE_ID=$IMAGE_ID" >> $GITHUB_ENV
+          echo "VERSION=$VERSION" >> $GITHUB_ENV
+
+      - name: Build docker image
+        run: |
+          docker build -t $IMAGE_ID:$VERSION .
+
+      - name: Push docker image
+        run: |
+          docker push $IMAGE_ID:$VERSION