code: func resolveCmdLine(cmd instructions.ShellDependantCmdLine, runConfig *container.Config, os, _, _ string) ([]string, bool) {
  	result := cmd.CmdLine
  	if cmd.PrependShell && result != nil {
  		result = append(getShell(runConfig, os), result...)
  	}
  	return result, false
  }
docs: // resolveCmdLine takes a command line arg set and optionally prepends a platform-specific
  // shell in front of it.