Impl: automatically publish releases to dockerhub (#3)

* update ignore lists
* action to build container and publish to dockerhub
* action run on each release
* update README with docker pull instructions

.dockerignore

@@ -0,0 +1,7 @@
+#by default ignore everything
+*
+
+#include the following
+!scripts
+!LICENSE
+!README.md

.github/workflows/docker.yml

@@ -0,0 +1,28 @@
+name: Build and Publish to DockerHub
+on:
+  release:
+    types: [published]
+
+jobs:
+  publish:
+    runs-on: ubuntu-latest
+    if: startsWith(github.ref, 'refs/tags/releases/')
+    steps:
+    - uses: actions/checkout@v2
+
+    - name: Docker Login - Docker Hub
+      uses: Azure/docker-login@v1
+      with:
+        username: ${{ secrets.DOCKER_USERNAME }}
+        password: ${{ secrets.DOCKER_PASSWORD }}
+    - name: Create Release tag
+      run: |
+        echo "bcliang/docker-libgourou" > BE_NAME
+        echo "${GITHUB_REF#refs/tags/releases/}" > RELEASE_TAG
+    - name: Build the Docker image
+      run: docker build . --file Dockerfile --tag $(cat BE_NAME):$(cat RELEASE_TAG)
+    - name: Tag to release + latest
+      run: | 
+        docker tag $(cat BE_NAME):$(cat RELEASE_TAG) $(cat BE_NAME):latest
+    - name: Push container to dockerhub
+      run: docker push --all-tags $(cat BE_NAME)

.gitignore

@@ -1,5 +1,8 @@
 # ignore binaries
 bin/
+adobe/
+Adobe-Digital-Editions/
+.adept/
 
 # ignore data files
 *.acsm

README.md

@@ -25,6 +25,12 @@ This container compiles the reference implementation utilities for libgourou (ma
 > docker build . -t bcliang/docker-libgourou
 ```
 
+### DockerHub
+
+```
+> docker pull bcliang/docker-libgourou:latest
+```
+
 ## Usage
 
 ### Automated download and de-drm