deploy.rb

task :check_revision do
  unless `git rev-parse HEAD` == `git rev-parse origin/master`
    puts ""
    puts " \033[1;33m**************************************************\033[0m"
    puts " \033[1;33m* WARNING: HEAD is not the same as origin/master *\033[0m"
    puts " \033[1;33m**************************************************\033[0m"
    puts ""
  end
end

before "cap:deploy", "check_revision"