#!/System/Library/Frameworks/Ruby.framework/Versions/Current/usr/bin/ruby -w
require 'optparse'

outfile = nil
version = nil

OptionParser.new do |opts|
  opts.banner = "Usage: #{File.basename(__FILE__)} [options]"
  opts.on_tail('-h', '--help', 'Show this message.') { puts opts; exit }

  opts.on("-o", "--output FILE", "Defaults to stdout.") do |file|
    outfile = file unless file == '-'
  end

  opts.on("-v", "--version NUMBER", "Version number section to extract.") do |arg|
    version = arg
  end
end.parse!

begin
  io = (outfile ? open(outfile, 'w') : STDOUT)

  echo = false

  while line = ARGF.gets
    if line =~ /^#+ .* \(v(.*)\)/
      return if echo
      echo = true if version.nil? || version == $1
    end
    io << line if echo
  end

  abort (version ? "Unable to find changes for version #{version}." : "Unable to find changes.") unless echo
rescue Errno::ENOENT => e
  abort "Unable to open output file: #{outfile || 'stdout'}: #{e}"
end