Generate 'Architectures' information (#472)

Enhance the `generate-stackbrew-library.sh` to generate `Architectures`
information.

Signed-off-by: Yihong Wang <yh.wang@ibm.com>

architectures

@@ -1,3 +1,3 @@
 bashbrew-arch   variants
-x64     alpine,onbuild,slim,wheezy
-ppc64le onbuild,slim
+amd64     default,alpine,onbuild,slim,wheezy
+ppc64le default,onbuild,slim

functions.sh

@@ -11,7 +11,7 @@ function get_arch() {
 	local arch
 	case $(uname -m) in
 	x86_64)
-		arch="x64"
+		arch="amd64"
 		;;
 	ppc64le)
 		arch="ppc64le"
@@ -40,3 +40,27 @@ function get_variants() {
 	variants=$(grep "$arch" architectures | sed -E 's/'"$arch"'\s*//' | sed -E 's/,/ /g')
 	echo "$variants"
 }
+
+# Get supported architectures for a specific version and variant
+#
+# Get default supported architectures from 'architectures'. Then go to the version folder
+# to see if there is a local architectures file. The local architectures will override the
+# default architectures. This will give us some benefits:
+# - a specific version may or may not support some architectures
+# - if there is no specialization for a version, just don't provide local architectures
+function get_supported_arches () {
+	local version
+	local variant
+	local arches
+	version="$1"; shift
+	variant="$1"; shift
+
+	# Get default supported arches
+	arches=$( grep "$variant" architectures 2>/dev/null | cut -d' ' -f1 )
+
+	# Get version specific supported architectures if there is specialized information
+	if [ -a "$version"/architectures ]; then
+		arches=$( grep "$variant" "$version"/architectures 2>/dev/null | cut -d' ' -f1 )
+	fi
+	echo "$arches"
+}

generate-stackbrew-library.sh

@@ -52,14 +52,17 @@ for version in "${versions[@]}"; do
 	fullVersion="$(grep -m1 'ENV NODE_VERSION ' "$version/Dockerfile" | cut -d' ' -f3)"
 
 	versionAliases=( $fullVersion $version ${stub} )
+	# Get supported architectures for a specific version. See details in function.sh
+	supportedArches=( $(get_supported_arches "$version" "default") )
 
 	echo "Tags: $(join ', ' "${versionAliases[@]}")"
+	echo "Architectures: $(join ', ' "${supportedArches[@]}")"
 	echo "GitCommit: ${commit}"
 	echo "Directory: ${version}"
 	echo
 
-        # Get supported variants according to the target architecture.
-        # See details in function.sh
+	# Get supported variants according to the target architecture.
+	# See details in function.sh
 	variants=$(get_variants | tr ' ' '\n')
 	for variant in $variants; do
 		# Skip non-docker directories
@@ -70,8 +73,12 @@ for version in "${versions[@]}"; do
 		slash='/'
 		variantAliases=( "${versionAliases[@]/%/-${variant//$slash/-}}" )
 		variantAliases=( "${variantAliases[@]//latest-/}" )
+		# Get supported architectures for a specific version and variant.
+		# See details in function.sh
+		supportedArches=( $(get_supported_arches "$version" "$variant") )
 
 		echo "Tags: $(join ', ' "${variantAliases[@]}")"
+		echo "Architectures: $(join ', ' "${supportedArches[@]}")"
 		echo "GitCommit: ${commit}"
 		echo "Directory: ${version}/${variant}"
 		echo

update.sh

@@ -35,7 +35,7 @@ function update_node_version {
 	(
 		cp "$template" "$dockerfile"
 		local fromprefix=
-		if [[ "$arch" != "x64" && "$variant" != "onbuild" ]]; then
+		if [[ "$arch" != "amd64" && "$variant" != "onbuild" ]]; then
 			fromprefix="$arch\/"
 		fi
 
@@ -55,8 +55,8 @@ for version in "${versions[@]}"; do
 
 	update_node_version "Dockerfile.template" "$version/Dockerfile"
 
-        # Get supported variants according the target architecture
-        # See details in function.sh
+	# Get supported variants according the target architecture
+	# See details in function.sh
 	variants=$(get_variants)
 
 	for variant in $variants; do