Bump to .NET 6. Add arm64 image build. Use short commit hash on image tag.

.github/workflows/build-image.yml

@@ -2,13 +2,15 @@
 
 on:
   push:
-    branches:
-      - 'dev'
 
 jobs:
   docker:
     name: Build Docker image 
     
+    strategy:
+      matrix: 
+        arch: ['amd64', 'arm64']
+    
     runs-on: ubuntu-latest
     steps:
       -
@@ -27,11 +29,17 @@ jobs:
           registry: ${{ secrets.REGISTRY_URL }}
           username: ${{ secrets.REGISTRY_USERNAME }}
           password: ${{ secrets.REGISTRY_PASSWORD }}
+      -
+        name: Get short commit SHA
+        id: commit_sha
+        run: echo "::set-output name=sha_short::$(git rev-parse --short HEAD)"
       -
         name: Build and push
         uses: docker/build-push-action@v2
         with:
           context: .
-          file: docker/Dockerfile.amd64
-          push: true
-          tags: ${{ secrets.REGISTRY_URL }}/west/telegram-bot:latest,${{ secrets.REGISTRY_URL }}/west/telegram-bot:${{ github.sha }}
+          file: docker/Dockerfile.${{ matrix.arch }}
+          platforms: linux/${{ matrix.arch }}
+          push: ${{ github.ref == 'refs/heads/dev' }}
+          tags: ${{ secrets.REGISTRY_URL }}/west/telegram-bot:latest,
+              |${{ secrets.REGISTRY_URL }}/west/telegram-bot:${{ steps.commit_sha.outputs.sha_short }}