update_usage

#!/usr/bin/env ruby

require 'pathname'

USAGE_REGEXP = /
  (?<open>#{Regexp.escape '<!--USAGE[-->'})
  .*
  (?<close>#{Regexp.escape '<!--]USAGE-->'})
/mx

path = Pathname('README.md')

original = path.read
changed = original.sub(USAGE_REGEXP) do
  m = Regexp.last_match
  system 'make -s blueutil'
  usage = `./blueutil --help`.sub(/\Ablueutil v.*/, '').lstrip
  "#{m[:open]}\n```\n#{usage}```\n#{m[:close]}"
end

path.open('w'){ |f| f.write(changed) } unless original == changed