Fix: private submodule cloning in GH action

Based on actions/checkout#287

Author: chizmeeple

.github/workflows/docker.branch.yml

@@ -3,29 +3,45 @@ name: docker-branch
 on:
   push:
     branches:
-      - '*'         # matches every branch that doesn't contain a '/'
-      - '*/*'       # matches every branch containing a single '/'
-      - '**'        # matches every branch
-      - '!master'   # excludes master
+      - "*" # matches every branch that doesn't contain a '/'
+      - "*/*" # matches every branch containing a single '/'
+      - "**" # matches every branch
+      - "!master" # excludes master
 
 jobs:
   main:
     runs-on: ubuntu-latest
     steps:
-      -
-        name: Set up QEMU
+      - name: Set up QEMU
         uses: docker/setup-qemu-action@v1
-      -
-        name: Set up Docker Buildx
+
+      - name: Set up Docker Buildx
         uses: docker/setup-buildx-action@v1
-      -
-        name: Login to DockerHub
+
+      - name: Login to DockerHub
         uses: docker/login-action@v1
         with:
           username: ${{ secrets.DOCKERHUB_USERNAME }}
           password: ${{ secrets.DOCKERHUB_TOKEN }}
-      - uses: actions/checkout@v2
-      - uses: benjlevesque/short-sha@v1.2
+
+      - name: clone main repository
+        uses: actions/checkout@v2
+
+      - name: clone submodule
+        uses: actions/checkout@v2
+        with:
+          repository: chiselwright/hydejack-pro
+          path: "#jekyll-theme-hydejack"
+          ssh-key: ${{ secrets.SSH_KEY }}
+          persist-credentials: true
+
+      - name: checkout submodule
+        run: |
+          git submodule init
+          git submodule update
+
+      - name: short sha
+        uses: benjlevesque/short-sha@v1.2
         id: short-sha
         with:
           length: 7
@@ -35,8 +51,8 @@ jobs:
       - run: echo $SHA
         env:
           SHA: ${{ env.SHA }}
-      -
-        name: Build and push
+
+      - name: build and push
         id: docker_build
         uses: docker/build-push-action@v2
         with:
@@ -45,6 +61,6 @@ jobs:
           build-args: |
             arg1=value1
             arg2=value2
-      -
-        name: Image digest
+
+      - name: image digest
         run: echo ${{ steps.docker_build.outputs.digest }}