docker: publish docker images to docker hub (#896)

docker: push dockerhub tags

* major.minor - tracks latest major.minor release (except major==0)
* latest - tracks official stable releases
* testing - tracks official stable releases or pre-releases (beta, rc)
* unstable - tracks nightly/unstable builds

.github/workflows/make.yml

@@ -46,6 +46,10 @@ jobs:
       # used to publish releases to GitHub by GoReleaser
       GITHUB_TOKEN: ${{ secrets.GH_TOKEN }}
 
+      # used to publish docker images
+      DOCKERHUB_USERNAME: ${{ secrets.DOCKERHUB_USERNAME }}
+      DOCKERHUB_TOKEN: ${{ secrets.DOCKERHUB_TOKEN }}
+
       # used in Azure tests
       KOPIA_AZURE_TEST_CONTAINER: ${{ secrets.KOPIA_AZURE_TEST_CONTAINER }}
       KOPIA_AZURE_TEST_STORAGE_ACCOUNT: ${{ secrets.KOPIA_AZURE_TEST_STORAGE_ACCOUNT }}
@@ -109,6 +113,12 @@ jobs:
     - name: Install macOS-specific packages
       run: "sudo xcode-select -r"
       if: ${{ contains(matrix.os, 'macos') }}
+    - name: Set up QEMU
+      uses: docker/setup-qemu-action@v1
+      if: ${{ contains(matrix.os, 'ubuntu') }}
+    - name: Set up Docker Buildx
+      uses: docker/setup-buildx-action@v1
+      if: ${{ contains(matrix.os, 'ubuntu') }}
     - name: Check out code into the Go module directory
       uses: actions/checkout@v2
       with: