Add basic "library.pl" script for generating "library/perl" file

This accepts an optional `--eol` flag to also include the EOL versions (with a big comment about removing them post-build).

Author: tianon

library.pl

@@ -0,0 +1,99 @@
+#!/usr/bin/env perl
+use 5.014;
+use strict;
+use warnings;
+use YAML::XS;
+
+my %arches = (
+	# https://github.com/docker-library/official-images/blob/master/library/debian
+	buster => 'amd64, arm32v7, arm64v8, i386, ppc64le, s390x',
+	stretch => 'amd64, arm32v7, arm64v8, i386',
+);
+
+print <<"END_HEADER";
+Maintainers: Peter Martini <PeterCMartini\@GMail.com> (\@PeterMartini),
+             Zak B. Elep <zakame\@cpan.org> (\@zakame)
+GitRepo: https://github.com/perl/docker-perl.git
+GitCommit: @{[ qx{ git log -1 --format=format:%H } ]}
+Architectures: $arches{buster}
+END_HEADER
+
+sub suffix {
+	my $suffix = shift;
+	return map { $_ eq 'latest' ? $suffix : $_ . '-' . $suffix } @_;
+}
+
+sub entry {
+	my $version = shift;
+	my $build = shift;
+	my $debian = shift;
+	my $eol = shift // 0;
+
+	my @versionAliases = ();
+
+	my @version = split /[.]/, $version;
+	for my $i (reverse 0 .. @version-1) {
+		push @versionAliases, join '.', @version[0 .. $i];
+	}
+
+	push @versionAliases, 'latest';
+
+	(my $buildSuffix = $build) =~ s/^main,//;
+	$buildSuffix =~ s/,/-/g;
+	my @buildAliases = ($build eq 'main' ? @versionAliases : suffix $buildSuffix, @versionAliases);
+
+	my @debianAliases = suffix $debian, @buildAliases;
+
+	my @aliases = ( ($eol ? () : @buildAliases), @debianAliases );
+
+	state %latest = ();
+	@aliases = grep { !defined $latest{$_} } @aliases;
+	@latest{ @aliases } = ( 1 ) x @aliases;
+
+	print <<~"END_ENTRY";
+
+	Tags: @{[ join ', ', @aliases ]}@{[ defined $arches{$debian} ? "\nArchitectures: $arches{$debian}" : '' ]}
+	Directory: @{[ ($eol ? 'eol/' : '') . sprintf '%i.%03i.%03i-%s-%s', @version, $build, $debian ]}
+	END_ENTRY
+}
+
+sub release {
+	my $release = shift;
+	my $builds = shift;
+	my $eol = shift // 0;
+
+	my @builds = (@$builds, map { "$_,threaded" } @$builds);
+
+	for my $build (@builds) {
+		for my $debian (reverse @{ $release->{debian_release} }) {
+			entry $release->{version}, $build, $debian, $eol;
+		}
+	}
+}
+
+my $config = do {
+	open my $fh, '<', 'config.yml' or die "Couldn't open config";
+	local $/;
+	Load <$fh>;
+};
+
+release $_, $config->{builds} for (reverse @{ $config->{releases} });
+
+exit unless @ARGV == 1 && $ARGV[0] eq '--eol';
+
+print <<END_EOL_COMMENT;
+
+#
+# THE FOLLOWING (EOL) TAGS ARE INTENDED AS A ONE-TIME BACKFILL/REBUILD
+#
+#   (they will be removed after they are successfully rebuilt)
+#
+END_EOL_COMMENT
+
+$config = do {
+	open my $fh, '<', 'eol/config.yml' or die "Couldn't open config";
+	local $/;
+	Load <$fh>;
+};
+
+release $_, $config->{builds}, 1 for (reverse @{ $config->{releases} });