code: func withEntrypointOverride(cmd []string, entrypoint []string) runConfigModifier {
  	return func(runConfig *container.Config) {
  		if len(cmd) > 0 {
  			runConfig.Entrypoint = entrypoint
  		}
  	}
  }
docs: // withEntrypointOverride sets an entrypoint on runConfig if the command is
  // not empty. The entrypoint is left unmodified if command is empty.
  //
  // The dockerfile RUN instruction expect to run without an entrypoint
  // so the runConfig entrypoint needs to be modified accordingly. ContainerCreate
  // will change a []string{""} entrypoint to nil, so we probe the cache with the
  // nil entrypoint.