figure out rails rollback STEP

gistfile1.txt

file_diffs = `bash -c "comm -23 <(git ls-tree -r --name-only #{ENV['environment']}/master:db/migrate) <(git ls-tree -r --name-only HEAD:db/migrate)"`.split
if file_diffs.size > 0
  puts "Need to do a db rollback before deploying branch"
  current_env_migrations = `git ls-tree -r --name-only #{ENV['environment']}/master:db/migrate`.split
  rollback_steps = current_env_migrations.drop_while { |e| !e[/#{file_diffs[0]}/] }.size
  puts "heroku run rake STEP=#{rollback_steps} db:rollback -a #{ENV['environment']}"
  `heroku run rake STEP=#{rollback_steps} db:rollback -a #{ENV['environment']}`
else
  puts "No db rollback necessary"
end