[linux/arm64] [linux/amd64] Use correct ref to commit message

Author: ianks

.github/workflows/ci.yml

@@ -44,7 +44,7 @@ jobs:
       PLATFORM: ${{ matrix.platform }}
       DOCKER_BUILD_PLATFORM: linux/${{ matrix.docker-platform-cpu }}
     steps:
-      - uses: actions/checkout@v2
+      - uses: actions/checkout@v3
 
       - name: Cache Docker layers
         uses: actions/cache@v3
@@ -73,7 +73,7 @@ jobs:
           bundle exec rake build:${PLATFORM} RCD_DOCKER_BUILD="$docker_build"
 
           # Save the image if the commit message contains the docker platform name (e.g. "[linux/arm64] ...")
-          if [[ "${{ github.event.head_commit.message }}" == *"[$DOCKER_BUILD_PLATFORM]"* ]]; then
+          if [[ "$(git log -1 --pretty=format:"%s")" == *"[$DOCKER_BUILD_PLATFORM]"* ]]; then
             echo "::info::Saving docker image $extra_tag"
             docker save -o "tmp/${extra_tag}.tar" $extra_tag
             echo "image-tarball=tmp/${extra_tag}.tar" >> $GITHUB_OUTPUT