def run!(cmd)
      cmd = @before_run_block.call(cmd) if @before_run_block
      return false unless cmd
      say "!txtgrn!> #{cmd}" unless Runfile.quiet
      exec cmd
    end
def run!(cmd)
      cmd = @before_run_block.call(cmd) if @before_run_block
      return false unless cmd
      say "!txtgrn!> #{cmd}" unless Runfile.quiet
      exec cmd
    end
Run a command, wait until it is done, then exit