Add initial "generate-stackbrew-library.sh" script

generate-stackbrew-library.sh

@@ -0,0 +1,77 @@
+#!/usr/bin/env bash
+set -Eeuo pipefail
+
+declare -A aliases=(
+	[3.1]='3 latest'
+	[2.12]='2'
+)
+
+self="$(basename "$BASH_SOURCE")"
+cd "$(dirname "$(readlink -f "$BASH_SOURCE")")"
+
+versions=( */ )
+versions=( "${versions[@]%/}" )
+
+# sort version numbers with highest first
+IFS=$'\n'; versions=( $(echo "${versions[*]}" | sort -rV) ); unset IFS
+
+# get the most recent commit which modified any of "$@"
+fileCommit() {
+	git log -1 --format='format:%H' HEAD -- "$@"
+}
+
+# get the most recent commit which modified "$1/Dockerfile" or any file COPY'd from "$1/Dockerfile"
+dirCommit() {
+	local dir="$1"; shift
+	(
+		cd "$dir"
+		fileCommit \
+			Dockerfile \
+			$(git show HEAD:./Dockerfile | awk '
+				toupper($1) == "COPY" {
+					for (i = 2; i < NF; i++) {
+						print $i
+					}
+				}
+			')
+	)
+}
+
+cat <<-EOH
+# this file is generated via https://github.com/tianon/docker-qemu/blob/$(fileCommit "$self")/$self
+
+Maintainers: Tianon Gravi <admwiggin@gmail.com> (@tianon)
+GitRepo: https://github.com/tianon/docker-qemu.git
+EOH
+
+# prints "$2$1$3$1...$N"
+join() {
+	local sep="$1"; shift
+	local out; printf -v out "${sep//%/%%}%s" "$@"
+	echo "${out#$sep}"
+}
+
+for version in "${versions[@]}"; do
+	commit="$(dirCommit "$version")"
+
+	fullVersion="$(git show "$commit":"$version/Dockerfile" | awk '$1 == "ENV" && $2 == "QEMU_VERSION" { print $3; exit }')"
+
+	rcVersion="${version%-rc}"
+
+	versionAliases=()
+	while [ "$fullVersion" != "$rcVersion" -a "${fullVersion%[.]*}" != "$fullVersion" ]; do
+		versionAliases+=( $fullVersion )
+		fullVersion="${fullVersion%[.]*}"
+	done
+	versionAliases+=(
+		$version
+		${aliases[$version]:-}
+	)
+
+	echo
+	cat <<-EOE
+		Tags: $(join ', ' "${versionAliases[@]}")
+		GitCommit: $commit
+		Directory: $version
+	EOE
+done