fix(ci): trigger docker image publish on automatic releases (#86)

.github/workflows/docker-image.yml

@@ -7,6 +7,10 @@ on:
       - 'main'
     tags:
       - 'v*'
+  workflow_run:
+    workflows: [Releaser]
+    types:
+      - completed
 
 # we want images in main to always build in-order, so main-latest always points
 # at the latest one but it is ok to build 'latest' and 'release' in parallel,
@@ -16,15 +20,37 @@ concurrency:
   cancel-in-progress: false
 
 jobs:
+  prepare_checkout:
+    if: (
+          github.repository == 'ipfs/bifrost-gateway'
+          || github.event_name == 'workflow_dispatch'
+        ) && (
+          github.event_name != 'workflow_run'
+          || github.event.workflow_run.conclusion == 'success'
+        )
+    name: Decide what ref to check out
+    runs-on: ubuntu-latest
+    outputs:
+      ref: ${{ github.event_name != 'workflow_run' && github.ref || steps.releaser.outputs.version }}
+    steps:
+      - name: Inspect triggering Releaser workflow run
+        id: releaser
+        if: github.event_name == 'workflow_run'
+        uses: protocol/.github/.github/actions/inspect-releaser@master
+        with:
+          artifacts-url: github.event.workflow_run.artifacts_url
   push_to_registry:
-    if: github.repository == 'ipfs/bifrost-gateway' || github.event_name == 'workflow_dispatch'
+    needs: [prepare_checkout]
+    if: needs.prepare_checkout.outputs.ref != ''
     name: Push Docker image to Docker Hub
     runs-on: ubuntu-latest
     env:
       IMAGE_NAME: ipfs/bifrost-gateway
     steps:
       - name: Check out the repo
         uses: actions/checkout@v3
+        with:
+          ref: ${{ needs.prepare_checkout.outputs.ref }}
 
       - name: Set up QEMU
         uses: docker/setup-qemu-action@v2