Add explicit multiarch support in "generate-stackbrew-library.sh"

Author: yosifkit

generate-stackbrew-library.sh

@@ -33,6 +33,22 @@ dirCommit() {
 	)
 }
 
+getArches() {
+	local repo="$1"; shift
+	local officialImagesUrl='https://github.com/docker-library/official-images/raw/master/library/'
+
+	eval "declare -A -g parentRepoToArches=( $(
+		find -name 'Dockerfile' -exec awk '
+				toupper($1) == "FROM" && $2 !~ /^('"$repo"'|scratch|microsoft\/[^:]+)(:|$)/ {
+					print "'"$officialImagesUrl"'" $2
+				}
+			' '{}' + \
+			| sort -u \
+			| xargs bashbrew cat --format '[{{ .RepoName }}:{{ .TagName }}]="{{ join " " .TagEntry.Architectures }}"'
+	) )"
+}
+getArches 'ruby'
+
 cat <<-EOH
 # this file is generated via https://github.com/docker-library/ruby/blob/$(fileCommit "$self")/$self
 
@@ -51,6 +67,9 @@ join() {
 for version in "${versions[@]}"; do
 	commit="$(dirCommit "$version")"
 
+	parent="$(awk 'toupper($1) == "FROM" { print $2 }' "$version/Dockerfile")"
+	arches="${parentRepoToArches[$parent]}"
+
 	fullVersion="$(git show "$commit":"$version/Dockerfile" | awk '$1 == "ENV" && $2 == "RUBY_VERSION" { print $3; exit }')"
 
 	versionAliases=(
@@ -62,6 +81,7 @@ for version in "${versions[@]}"; do
 	echo
 	cat <<-EOE
 		Tags: $(join ', ' "${versionAliases[@]}")
+		Architectures: $(join ', ' $arches)
 		GitCommit: $commit
 		Directory: $version
 	EOE
@@ -74,9 +94,18 @@ for version in "${versions[@]}"; do
 		variantAliases=( "${versionAliases[@]/%/-$variant}" )
 		variantAliases=( "${variantAliases[@]//latest-/}" )
 
+		case "$variant" in
+			onbuild) variantArches="$arches" ;;
+			*)
+				variantParent="$(awk 'toupper($1) == "FROM" { print $2 }' "$version/$variant/Dockerfile")"
+				variantArches="${parentRepoToArches[$variantParent]}"
+				;;
+		esac
+
 		echo
 		cat <<-EOE
 			Tags: $(join ', ' "${variantAliases[@]}")
+			Architectures: $(join ', ' $variantArches)
 			GitCommit: $commit
 			Directory: $version/$variant
 		EOE