Use goreleaser to build weekly releases (grafana/phlare#576)

Those releases power the Grafana Labs internal roll-outs, that occur
weekly into our production systems.

Goreleaser is used to build those releases with the same config that is
used for the project releases.

To get around some limitations around semver in goreleaser we have to
imitate a version with local git tags.

.github/workflows/weekly-release.yml

@@ -0,0 +1,69 @@
+name: goreleaser-weekly
+
+on:
+  push:
+    branches:
+      - 'weekly/f*'
+jobs:
+  goreleaser-weekly:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v3
+        with:
+          fetch-depth: 0
+      - name: Set GORELEASER_CURRENT_TAG
+        run: echo "GORELEASER_CURRENT_TAG=v0.0.0-$(./tools/image-tag)" >> $GITHUB_ENV
+      - name: Set WEEKLY_IMAGE_TAG
+        run: echo "WEEKLY_IMAGE_TAG=$(./tools/image-tag)" >> $GITHUB_ENV
+      # Forces goreleaser to use the correct previous tag for the changelog
+      - name: Set GORELEASER_PREVIOUS_TAG
+        run: echo "GORELEASER_PREVIOUS_TAG=$(git tag -l --sort=-version:refname | grep -E '^weekly-.*' | head -n 2 | tail -1)" >> $GITHUB_ENV
+      - run: git fetch --force --tags
+      - name: Create tags for this weekly release
+        run: |
+          git tag "$GORELEASER_CURRENT_TAG"
+          git tag "$WEEKLY_IMAGE_TAG"
+      - uses: actions/setup-go@v3
+        with:
+          go-version: ">=1.19.5"
+          cache: true
+      # setup docker buildx
+      - name: Set up QEMU
+        uses: docker/setup-qemu-action@v2
+      - name: Set up Docker Buildx
+        uses: docker/setup-buildx-action@v2
+      # login to docker hub
+      - uses: docker/login-action@v2
+        name: Login to Docker Hub
+        with:
+          username: ${{ secrets.DOCKERHUB_USERNAME }}
+          password: ${{ secrets.DOCKERHUB_TOKEN }}
+      - uses: goreleaser/goreleaser-action@v4
+        with:
+          # either 'goreleaser' (default) or 'goreleaser-pro':
+          distribution: goreleaser
+          version: latest
+          args: release --clean --skip-publish
+        env:
+          GITHUB_TOKEN: ${{ secrets.GH_BOT_ACCESS_TOKEN }}
+          # Your GoReleaser Pro key, if you are using the 'goreleaser-pro'
+          # distribution:
+          # GORELEASER_KEY: ${{ secrets.GORELEASER_KEY }}
+          #
+      - name: Push per architecture images and create multi-arch manifest
+        run: |
+          set +x
+          IMAGE_AMMENDS=()
+
+          # the grep needs to remove an extra v, which is in the git tag, but not in the image tag
+          for image in $(docker images --format '{{.Repository}}:{{.Tag}}' | grep "grafana/phlare:${GORELEASER_CURRENT_TAG:1}-"); do
+            new_image="${image/0.0.0-/}"
+            docker tag "${image}" "${new_image}"
+            docker push "${new_image}"
+            IMAGE_AMMENDS+=( "--amend" "${new_image}" )
+          done
+
+          docker manifest create "grafana/phlare:${WEEKLY_IMAGE_TAG}" "${IMAGE_AMMENDS[@]}"
+          docker manifest push "grafana/phlare:${WEEKLY_IMAGE_TAG}"
+      - name: Push git tag for weekly release
+        run: git push https://grafanabot:${{ secrets.GH_BOT_ACCESS_TOKEN }}@github.com/grafana/phlare.git "${WEEKLY_IMAGE_TAG}"