Refactor multiarch support to go all the way to correct Architectures lines in "generate-stackbrew-library.sh"

Author: tianon

generate-stackbrew-library.sh

@@ -37,6 +37,22 @@ dirCommit() {
 	)
 }
 
+getArches() {
+	local repo="$1"; shift
+	local officialImagesUrl='https://github.com/docker-library/official-images/raw/master/library/'
+
+	eval "declare -g -A parentRepoToArches=( $(
+		find -name 'Dockerfile' -exec awk '
+				toupper($1) == "FROM" && $2 !~ /^('"$repo"'|scratch|microsoft\/[^:]+)(:|$)/ {
+					print "'"$officialImagesUrl"'" $2
+				}
+			' '{}' + \
+			| sort -u \
+			| xargs bashbrew cat --format '[{{ .RepoName }}:{{ .TagName }}]="{{ join " " .TagEntry.Architectures }}"'
+	) )"
+}
+getArches 'openjdk'
+
 cat <<-EOH
 # this file is generated via https://github.com/docker-library/openjdk/blob/$(fileCommit "$self")/$self
 
@@ -102,9 +118,13 @@ for version in "${versions[@]}"; do
 
 	fullVersion="$(git show "$commit":"$version/Dockerfile" | awk '$1 == "ENV" && $2 == "JAVA_VERSION" { gsub(/~/, "-", $3); print $3; exit }')"
 
+	parent="$(awk 'toupper($1) == "FROM" { print $2 }' "$version/Dockerfile")"
+	arches="${parentRepoToArches[$parent]}"
+
 	echo
 	cat <<-EOE
 		Tags: $(join ', ' $(aliases "$javaVersion" "$javaType" "$fullVersion"))
+		Architectures: $(join ', ' $arches)
 		GitCommit: $commit
 		Directory: $version
 	EOE
@@ -122,9 +142,18 @@ for version in "${versions[@]}"; do
 
 		fullVersion="$(git show "$commit":"$dir/Dockerfile" | awk '$1 == "ENV" && $2 == "JAVA_VERSION" { gsub(/~/, "-", $3); print $3; exit }')"
 
+		case "$v" in
+			windows/*) variantArches='windows-amd64' ;;
+			*)
+				variantParent="$(awk 'toupper($1) == "FROM" { print $2 }' "$version/$v/Dockerfile")"
+				variantArches="${parentRepoToArches[$variantParent]}"
+				;;
+		esac
+
 		echo
 		cat <<-EOE
 			Tags: $(join ', ' $(aliases "$javaVersion" "$javaType" "$fullVersion" "$variant"))
+			Architectures: $(join ', ' $variantArches)
 			GitCommit: $commit
 			Directory: $dir
 		EOE