run rails with thin and tail -f for development.log that outputs rails logs to the console

run.rb

require 'thread'

log='log/development.log'
system "truncate --size 0 #{log}"

Thread.new do
  system('bundle exec thin start')
end

args = %W{tail -f #{log}} + [:err => [:child, :out]]

IO.popen(args) do |io|
  while line = io.gets
    puts line
  end
end