import org.eclipse.jgit.transport.PreReceiveHook; //导入依赖的package包/类
@Override
public void init(Project.NameKey project, ReceivePack rp) {
  ProjectState ps = projectCache.get(project);
  if (!ps.isEnableSignedPush()) {
    rp.setSignedPushConfig(null);
    return;
  } else if (signedPushConfig == null) {
    log.error(
        "receive.enableSignedPush is true for project {} but"
            + " false in gerrit.config, so signed push verification is"
            + " disabled",
        project.get());
    rp.setSignedPushConfig(null);
    return;
  }
  rp.setSignedPushConfig(signedPushConfig);

  List<PreReceiveHook> hooks = new ArrayList<>(3);
  if (ps.isRequireSignedPush()) {
    hooks.add(SignedPushPreReceiveHook.Required.INSTANCE);
  }
  hooks.add(hook);
  hooks.add(rp.getPreReceiveHook());
  rp.setPreReceiveHook(PreReceiveHookChain.newChain(hooks));
}