Introduce additional docker tags for the debian version.

* Added new docker tag variations to specify the debian version ('stretch', and 'buster').
* Arch images are alway as specific as possible: pihole/pihole:master-amd64-stretch
* Multiarch images have both the specific debian version tags as well as the generic non-debian tags: pihole/pihole:master-stretch & pihole/pihole:master
* Currently, the non-specific tags point to the 'stretch' images. Eventaully it can be migrated to 'buster'.
* Use GitHub actions to do the builds. Although the script names include 'gh-actions' to differentiate them from the 'circle' scripts, there is zero logic that is specific to Github (ie. no Github environment variables).
* 'armhf:buster' & 'arm64:buster' has an issue with `ip route get`. I think the issue is related to 'qemu', but I'm not sure. Update the `validate_env` function to only use `ip route get` if `nc` reports something strange.

Signed-off-by: Daniel <daniel@developerdan.com>

.github/workflows/test-and-build.yaml

@@ -0,0 +1,62 @@
+name: Test & Build
+on:
+  push:
+    branches:
+      - master
+      - dev
+      - v*
+      - beta-v*
+  pull_request:
+
+#env:
+#  DOCKER_HUB_REPO: pihole
+
+jobs:
+  test-and-build:
+    runs-on: ubuntu-latest
+    strategy:
+      fail-fast: false
+      matrix:
+        ARCH: [amd64, armhf, arm64]
+        DEBIAN_VERSION: [stretch, buster]
+    env:
+      ARCH: ${{matrix.ARCH}}
+      DEBIAN_VERSION: ${{matrix.DEBIAN_VERSION}}
+    steps:
+      - name: Checkout Repo
+        uses: actions/checkout@v2
+      - name: Run Tests
+        run: |
+          echo "Building ${ARCH}-${DEBIAN_VERSION}"
+          ./gh-actions-test.sh
+      - name: Push the ARCH image
+        if: github.event_name != 'pull_request'
+        run: |
+          . gh-actions-vars.sh
+          echo "${{ secrets.DOCKERHUB_PASS }}" | docker login --username="${{ secrets.DOCKERHUB_USER }}" --password-stdin
+          docker push "${ARCH_IMAGE}"
+      - name: Upload gh-workspace
+        if: github.event_name != 'pull_request'
+        uses: actions/upload-artifact@v1
+        with:
+          name: gh-workspace
+          path: .gh-workspace
+
+  publish:
+    if: github.event_name != 'pull_request'
+    runs-on: ubuntu-latest
+    needs: test-and-build
+    steps:
+      - name: Checkout Repo
+        uses: actions/checkout@v2
+      - name: Download workspace files
+        uses: actions/download-artifact@v1
+        with:
+          name: gh-workspace
+          path: .gh-workspace
+      - name: Tag and Publish multi-arch images
+        env:
+          DOCKERHUB_PASS: ${{ secrets.DOCKERHUB_PASS }}
+          DOCKERHUB_USER: ${{ secrets.DOCKERHUB_USER }}
+        run: |
+          ./gh-actions-deploy.sh