Create docker-snapshot.yml (#43)

* Create docker-snapshot.yml

* Update docker-snapshot.yml

* Update docker-snapshot.yml

* Update docker-snapshot.yml

* Update docker-snapshot.yml

.github/workflows/docker-snapshot.yml

@@ -0,0 +1,38 @@
+name: Daily Docker Snapshot
+on:
+  schedule: #to be pushed daily, at 07:00 PM (19:00)
+    - cron: '0 19 * * *' #NOTE: Only works if the workflow file is present in the default branch
+jobs:
+  Pushing-Docker-Image:
+    runs-on: ubuntu-latest
+    steps:
+    - uses: actions/checkout@v2
+      with:
+        ref: develop #pushing the image from the develop branch
+
+    - name: Setting Up Docker Buildx #used for caching image layers, improves performance
+      id: buildx
+      uses: docker/setup-buildx-action@v1
+
+    - name: Login to Docker Hub
+      uses: docker/login-action@v1
+      with: 
+        username: ${{ secrets.DOCKER_HUB_USERNAME }}
+        password: ${{ secrets.DOCKER_HUB_ACCESS_TOKEN }}
+
+    - name: Get and Set Version
+      run: |
+        source ci/set-docker-image-version.sh
+        echo "version=${DOCKER_IMG_VER}" >> $GITHUB_ENV
+
+    - name: Build and push
+      uses: docker/build-push-action@v2
+      with:
+        context: .
+        builder: ${{ steps.buildx.outputs.name }}
+        file: ./Dockerfile
+        push: true
+        tags: ga4gh/ga4gh-starter-kit-common:snapshot #The docker image is tagged :snapshot
+        build-args: VERSION=${{ env.version }}
+        cache-from: type=gha #GitHub Actions Cache Exporter
+        cache-to: type=gha,mode=max