Build a docker hub release for tag names too

Closes: https://github.com/bgp/stayrtr/issues/80
Closes: https://github.com/bgp/stayrtr/issues/19

.github/workflows/docker-tag.yml

@@ -0,0 +1,67 @@
+name: Tagged docker build
+
+on:
+  push:
+    tags:
+      - 'v*'
+
+
+jobs:
+  build:
+    runs-on: ubuntu-latest
+    steps:
+      - name: Get short SHA from commit hash
+        id: shacalc
+        run: echo "::set-output name=tagname::$(git describe --tags --abbrev=0 HEAD)"
+
+      - name: Check Out Repo
+        uses: actions/checkout@v2
+
+      - name: Login to Docker Hub
+        uses: docker/login-action@v1
+        with:
+          username: ${{ secrets.DOCKER_HUB_USERNAME }}
+          password: ${{ secrets.DOCKER_HUB_ACCESS_TOKEN }}
+
+      - name: Set up Docker Buildx
+        id: buildx
+        uses: docker/setup-buildx-action@v1
+
+      - name: Build and push (stayrtr)
+        id: docker_build_stayrtr
+        uses: docker/build-push-action@v2
+        with:
+          context: ./
+          file: ./Dockerfile
+          push: true
+          tags: rpki/stayrtr:latest,rpki/stayrtr:${{ steps.shacalc.outputs.tagname }}
+          target: stayrtr
+
+      - name: Image digest (stayrtr)
+        run: echo ${{ steps.docker_build_stayrtr.outputs.digest }}
+
+      - name: Build and push (rtrmon)
+        id: docker_build_rtrmon
+        uses: docker/build-push-action@v2
+        with:
+          context: ./
+          file: ./Dockerfile
+          push: true
+          tags: rpki/rtrmon:latest,rpki/rtrmon:${{ steps.shacalc.outputs.tagname }}
+          target: rtrmon
+
+      - name: Image digest (rtrmon)
+        run: echo ${{ steps.docker_build_rtrmon.outputs.digest }}
+
+      - name: Build and push rtrdump
+        id: docker_build_rtrdump
+        uses: docker/build-push-action@v2
+        with:
+          context: ./
+          file: ./Dockerfile
+          push: true
+          tags: rpki/rtrdump:latest,rpki/rtrdump:${{ steps.shacalc.outputs.tagname }}
+          target: rtrdump
+
+      - name: Image digest (rtrdump)
+        run: echo ${{ steps.docker_build_rtrdump.outputs.digest }}