✨ Support building multi-platform images

Dockerfile

@@ -4,7 +4,7 @@ LABEL "maintainer"="Lars Gohr"
 
 RUN apk update \
   && apk upgrade \
-  && apk add --no-cache git
+  && apk add --no-cache git sudo
 
 ADD entrypoint.sh /entrypoint.sh
 ENTRYPOINT ["/entrypoint.sh"]
@@ -14,6 +14,7 @@ RUN apk add --no-cache coreutils bats
 ADD test.bats /test.bats
 ADD mock.sh /usr/local/bin/docker
 ADD mock.sh /usr/bin/date
+ADD mock.sh /usr/bin/sudo
 RUN /test.bats
 
 FROM runtime

README.md

@@ -188,6 +188,17 @@ with:
   no_push: ${{ github.event_name == 'push' }}
 ```
 
+### platforms
+Use `platforms` when you want to build a multi-platform image (separated by comma).
+
+```yaml
+with:
+  name: myDocker/repository
+  username: ${{ secrets.DOCKER_USERNAME }}
+  password: ${{ secrets.DOCKER_PASSWORD }}
+  platforms: linux/amd64,linux/arm64
+```
+
 ### Tags
 
 This action supports multiple options that tags are handled.  

action.yml

@@ -44,6 +44,9 @@ inputs:
   tags:
     description: 'Use tags when you want to bring your own tags (separated by comma)'
     required: false
+  platforms:
+    description: 'Use platforms to build multi-platform images (separated by comma)'
+    required: false
   tag_names:
     description: 'Use tag_names when you want to push tags/release by their git name'
     required: false

entrypoint.sh

@@ -16,6 +16,10 @@ main() {
     sanitize "${INPUT_PASSWORD}" "password"
   fi
 
+  if uses "${INPUT_PLATFORMS}"; then
+    enableExperimentalDocker
+  fi
+
   registryToLower
   nameToLower
 
@@ -84,6 +88,11 @@ sanitize() {
   fi
 }
 
+enableExperimentalDocker() {
+  echo $'{"experimental": true}' | sudo dd status=none of=/etc/docker/daemon.json
+  sudo service docker restart
+}
+
 registryToLower(){
  INPUT_REGISTRY=$(echo "${INPUT_REGISTRY}" | tr '[A-Z]' '[a-z]')
 }
@@ -190,7 +199,12 @@ build() {
   for TAG in ${TAGS}; do
     BUILD_TAGS="${BUILD_TAGS}-t ${INPUT_NAME}:${TAG} "
   done
-  docker build ${INPUT_BUILDOPTIONS} ${BUILDPARAMS} ${BUILD_TAGS} ${CONTEXT}
+  if uses "${INPUT_PLATFORMS}"; then
+    local PLATFORMS="--platform ${INPUT_PLATFORMS}"
+    docker buildx build ${PLATFORMS} ${INPUT_BUILDOPTIONS} ${BUILDPARAMS} ${BUILD_TAGS} ${CONTEXT}
+  else
+    docker build ${INPUT_BUILDOPTIONS} ${BUILDPARAMS} ${BUILD_TAGS} ${CONTEXT}
+  fi
 }
 
 push() {

test.bats

@@ -6,6 +6,7 @@ setup(){
 
   declare -A -p MOCK_RETURNS=(
   ['/usr/local/bin/docker']=""
+  ['sudo']=""
   ) > mockReturns
 
   export GITHUB_REF='refs/heads/master'
@@ -20,6 +21,7 @@ teardown() {
   unset INPUT_DOCKERFILE
   unset INPUT_REGISTRY
   unset INPUT_CACHE
+  unset INPUT_PLATFORMS
   unset GITHUB_SHA
   unset INPUT_PULL_REQUESTS
   unset MOCK_ERROR_CONDITION
@@ -654,6 +656,24 @@ teardown() {
 /usr/local/bin/docker logout"
 }
 
+@test "it supports building multiple platforms" {
+  export GITHUB_REF='refs/heads/main'
+  export INPUT_PLATFORMS='linux/amd64,linux/arm64'
+
+  run /entrypoint.sh
+
+  expectStdOutContains "::set-output name=tag::latest"
+
+  expectMockCalledContains "/usr/bin/sudo dd status=none of=/etc/docker/daemon.json
+/usr/bin/sudo service docker restart
+/usr/local/bin/docker login -u USERNAME --password-stdin
+/usr/local/bin/docker buildx build --platform linux/amd64,linux/arm64 -t my/repository:latest .
+/usr/local/bin/docker push my/repository:latest
+/usr/local/bin/docker inspect --format={{index .RepoDigests 0}} my/repository:latest
+/usr/local/bin/docker logout"
+  expectMockArgs '/usr/bin/sudo {"experimental": true}'
+}
+
 expectStdOutIs() {
   local expected=$(echo "${1}" | tr -d '\n')
   local got=$(echo "${output}" | tr -d '\n')