From b993bc09556935e1c0b9bc685bf9da4b1115a331 Mon Sep 17 00:00:00 2001
From: Hugh Nimmo-Smith <hughns@element.io>
Date: Thu, 19 Jan 2023 17:07:55 +0000
Subject: [PATCH] Build docker image for multiple architectures including ARM

This is based on https://www.docker.com/blog/faster-multi-platform-builds-dockerfile-cross-compilation-guide/ which doesn't use QEMU
---
 .github/workflows/docker-publish.yml | 4 ++++
 Dockerfile                           | 4 ++--
 doc/docker.md                        | 4 +++-
 3 files changed, 9 insertions(+), 3 deletions(-)

diff --git a/.github/workflows/docker-publish.yml b/.github/workflows/docker-publish.yml
index dad55339..a70eea6c 100644
--- a/.github/workflows/docker-publish.yml
+++ b/.github/workflows/docker-publish.yml
@@ -23,6 +23,9 @@ jobs:
       - name: Checkout repository
         uses: actions/checkout@v3
 
+      - name: Set up Docker Buildx
+        uses: docker/setup-buildx-action@v2
+
       - name: Log into registry ${{ env.REGISTRY }}
         uses: docker/login-action@v2
         with:
@@ -42,3 +45,4 @@ jobs:
           push: ${{ github.event_name != 'pull_request' }}
           tags: ${{ steps.meta.outputs.tags }}
           labels: ${{ steps.meta.outputs.labels }}
+          platforms: linux/amd64,linux/arm64,linux/arm/v7
diff --git a/Dockerfile b/Dockerfile
index f35dc559..4d8be56b 100644
--- a/Dockerfile
+++ b/Dockerfile
@@ -1,4 +1,4 @@
-FROM docker.io/node:alpine as builder
+FROM --platform=${BUILDPLATFORM} docker.io/node:alpine as builder
 RUN apk add --no-cache git python3 build-base
 
 WORKDIR /app
@@ -10,7 +10,7 @@ RUN yarn install
 COPY . /app
 RUN yarn build
 
-FROM docker.io/nginx:alpine
+FROM --platform=${BUILDPLATFORM} docker.io/nginx:alpine
 
 # Copy the dynamic config script
 COPY ./docker/dynamic-config.sh /docker-entrypoint.d/99-dynamic-config.sh
diff --git a/doc/docker.md b/doc/docker.md
index db779fe1..752c492f 100644
--- a/doc/docker.md
+++ b/doc/docker.md
@@ -35,7 +35,9 @@ To stop the container, simply hit `ctrl+c`.
 
 In this repository, create a Docker image:
 
-```
+```sh
+# Enable BuildKit https://docs.docker.com/develop/develop-images/build_enhancements/
+export DOCKER_BUILDKIT=1
 docker build -t hydrogen .
 ```