Publish images to GitHub Container Registry (#146)

Push Docker images to both Docker Hub and the repo's container registry
on GitHub - GHCR's rate limits are much more generous than Docker Hub's.

scripts/BUILD

@@ -1,5 +1,17 @@
+genrule(
+    name = "default_docker_repo",
+    outs = ["default_docker_repo"],
+    cmd = f'echo -n "{CONFIG.DEFAULT_DOCKER_REPO}" > $OUTS',
+)
+
 for script in glob(["*.sh"]):
     sh_binary(
         name = basename(splitext(script)[0]),
+        data = [
+            ":default_docker_repo",
+        ],
         main = script,
+        deps = [
+            "//third_party/sh:shflags",
+        ],
     )

scripts/publish-images.sh

@@ -1,8 +1,39 @@
 #!/bin/bash
+
+# This script uploads Dracon container images to Docker Hub, as well as the GitHub Container
+# Registry if the script is being executed by a GitHub action.
+
 set -eo pipefail
 
+set +e
+source "$PWD/plz-out/gen/third_party/sh/shflags"
+set -e
+
+DEFINE_boolean dry_run "$FLAGS_FALSE" "Echo the Docker commands that would be run, rather than actually running them"
+
+FLAGS "$@" || exit 1
+eval set -- "$FLAGS_ARGV"
+
+if [ "$FLAGS_dry_run" -eq "$FLAGS_TRUE" ]; then
+  docker="echo docker"
+else
+  docker=docker
+fi
+
+default_repo="$(cat plz-out/gen/scripts/default_docker_repo)"
+
+if [ -n "$GITHUB_REPOSITORY" ] && [ -n "$GITHUB_ACTOR" ] && [ -n "$GITHUB_TOKEN" ]; then
+  ghcr_root="ghcr.io/$GITHUB_REPOSITORY"
+fi
+
 if [ -n "${DOCKERHUB_USERNAME}" ]; then
-  echo "${DOCKERHUB_PASSWORD}" | docker login --username "${DOCKERHUB_USERNAME}" --password-stdin
+  echo "Authorising with Docker Hub"
+  echo "${DOCKERHUB_PASSWORD}" | $docker login --username "${DOCKERHUB_USERNAME}" --password-stdin
+fi
+
+if [ -n "$ghcr_root" ]; then
+  echo "Authorising with GitHub Container Registry"
+  echo "$GITHUB_TOKEN" | $docker login ghcr.io --username "$GITHUB_ACTOR" --password-stdin
 fi
 
 version=$(git describe --always)
@@ -14,16 +45,26 @@ fqns_to_push=()
 export DOCKER_BUILDKIT=1
 for rule in ${docker_rules}; do
   ./pleasew run "${rule}_load"
+
   fqn=$(cat $(./pleasew build "${rule}_fqn" | tail -n1 | tr -s " "))
   repo="$(echo "${fqn}" | cut -f1 -d\:)"
   fqn_version="${repo}:${version}"
   echo ""
   echo "-> tagging as ${fqn_version}"
-  docker tag "${fqn}" "${fqn_version}"
+  $docker tag "${fqn}" "${fqn_version}"
   fqns_to_push+=("${fqn_version}")
+
+  if [ -n "$ghcr_root" ]; then
+    fqn="${fqn/$default_repo/$ghcr_root}"
+    repo="$(echo "${fqn}" | cut -f1 -d\:)"
+    fqn_version="${repo}:${version}"
+    echo "-> tagging as ${fqn_version}"
+    $docker tag "${fqn}" "${fqn_version}"
+    fqns_to_push+=("${fqn_version}")
+  fi
 done
 
 for fqn_to_push in "${fqns_to_push[@]}"; do
   echo "-> pushing as ${fqn_to_push}"
-  docker push "${fqn_to_push}"
+  $docker push "${fqn_to_push}"
 done