Support versioned Docker builds (#1799)

.github/workflows/docker-deploy.yml

@@ -1,12 +1,22 @@
 name: Deploy docker
-on: [push]
-env:
-  DEPLOY_NAME: gollumwiki/gollum:latest
+on:
+  push:
+    branches:
+      - master
+  release:
+      types: [published]
 jobs:
   build:
     runs-on: ubuntu-latest
-    if: ${{ github.ref == 'refs/heads/master' }}
     steps:
+      - name: Set deploy name to master
+        if: github.ref == 'refs/heads/master'
+        run: |
+          echo "DEPLOY_NAME=gollumwiki/gollum:master"
+      - name: Set deploy name to release version
+        if: startsWith(github.ref, 'refs/tags/')
+        run: |
+          echo "DEPLOY_NAME=gollumwiki/gollum:${{ github.ref_name }}"
       - name: Check Out Repo
         uses: actions/checkout@v2
       - name: Login
@@ -36,4 +46,4 @@ jobs:
           cache-from: type=local,src=/tmp/.buildx-cache
           cache-to: type=local,dest=/tmp/.buildx-cache
       - name: Image digest
-        run: echo ${{ steps.docker_build.outputs.digest }}
+        run: echo ${{ steps.docker_build.outputs.digest }}