Update "versions" curl invocation to be more defensive

This allows the script to differentiate 404 from 503 so that we are less likely to accidentally commit downgrades for temporary failures.

versions.sh

@@ -23,8 +23,22 @@ else
 fi
 versions=( "${versions[@]%/}" )
 
+scriptPid="$$" # so we can kill the script even from a subshell
+_curl() {
+	exec 42>&1
+	local code
+	code="$(curl --silent --location -o /dev/fd/42 --write-out '%{http_code}' "$@")"
+	case "$code" in
+		200) return 0 ;;
+		404) return 1 ;;
+	esac
+	echo >&2 "error: unexpected status code $code while fetching: $*"
+	kill "$scriptPid"
+	exit 1
+}
+
 dindLatest="$(
-	curl -fsSL -H 'Accept: application/json' 'https://github.com/docker/docker/commits/master/hack/dind.atom' \
+	_curl -H 'Accept: application/json' 'https://github.com/docker/docker/commits/master/hack/dind.atom' \
 		| jq -r '.payload | first(.commitGroups[].commits[].oid)'
 )"
 
@@ -75,7 +89,7 @@ buildxVersions="$(
 buildx=
 buildxVersion=
 for buildxVersion in $buildxVersions; do
-	if checksums="$(curl -fsSL "https://github.com/docker/buildx/releases/download/v${buildxVersion}/checksums.txt")"; then
+	if checksums="$(_curl "https://github.com/docker/buildx/releases/download/v${buildxVersion}/checksums.txt")"; then
 		buildx="$(jq <<<"$checksums" -csR --arg version "$buildxVersion" '
 			rtrimstr("\n") | split("\n")
 			| map(
@@ -127,7 +141,7 @@ composeVersions="$(
 compose=
 composeVersion=
 for composeVersion in $composeVersions; do
-	if checksums="$(curl -fsSL "https://github.com/docker/compose/releases/download/v${composeVersion}/checksums.txt")"; then
+	if checksums="$(_curl "https://github.com/docker/compose/releases/download/v${composeVersion}/checksums.txt")"; then
 		compose="$(jq <<<"$checksums" -csR --arg version "$composeVersion" '
 			rtrimstr("\n") | split("\n")
 			| map(
@@ -223,7 +237,7 @@ for version in "${versions[@]}"; do
 			windows-*) url="https://download.docker.com/win/static/$channel/$arch/docker-$fullVersion.zip"; windows=1 ;;
 			*) url="https://download.docker.com/linux/static/$channel/$arch/docker-$fullVersion.tgz"; windows= ;;
 		esac
-		if wget --quiet --spider "$url" &> /dev/null; then
+		if _curl --head "$url" > /dev/null; then
 			export bashbrewArch url
 			doc="$(
 				jq <<<"$doc" -c '.arches[env.bashbrewArch] = {
@@ -245,7 +259,7 @@ for version in "${versions[@]}"; do
 		case "$bashbrewArch" in
 			amd64 | arm64v8)
 				rootlessExtrasUrl="https://download.docker.com/linux/static/$channel/$arch/docker-rootless-extras-$fullVersion.tgz"
-				if wget --quiet --spider "$rootlessExtrasUrl" &> /dev/null; then
+				if _curl --head "$rootlessExtrasUrl" > /dev/null; then
 					export rootlessExtrasUrl
 					doc="$(jq <<<"$doc" -c '
 						.arches[env.bashbrewArch].rootlessExtrasUrl = env.rootlessExtrasUrl