Pull Requests (PRs) that are neither progressed nor resolved clutter the list of PRs, making it difficult for the maintainers to manage and prioritize unresolved PRs. To automatically track, follow up, and close such inactive PRs, Stale bot was introduced by GitHub. Despite its increasing adoption, there are ongoing debates on whether using Stale bot alleviates or exacerbates the problem of inactive PRs. To better understand if and how Stale bot helps projects in their pull-based development workflow, we perform an empirical study of 20 large and popular open-source projects. We find that Stale bot can help deal with a backlog of unresolved PRs as the projects closed more PRs within the first few months of adoption. Moreover, Stale bot can help improve the efficiency of the PR review process as the projects reviewed PRs that ended up merged and resolved PRs that ended up closed faster after the adoption. However, Stale bot can also negatively affect the contributors as the projects experienced a considerable decrease in their number of active contributors after the adoption. Therefore, relying solely on Stale bot to deal with inactive PRs may lead to decreased community engagement and an increased probability of contributor abandonment.

翻译：既未被推进也未解决的拉取请求（PR）会杂乱地堆砌在PR列表中，使维护者难以管理和优先处理未解决的PR。为自动跟踪、跟进并关闭此类非活跃PR，GitHub引入了Stale Bot。尽管其采用率不断增加，但关于使用Stale Bot是缓解还是加剧非活跃PR问题的争论仍在持续。为更深入了解Stale Bot是否以及如何帮助项目在基于拉取请求的开发流程中发挥作用，我们对20个大型开源项目进行了实证研究。我们发现，Stale Bot有助于处理积压的未解决PR，因为在采用该工具的最初几个月内，项目关闭了更多PR。此外，Stale Bot能提升PR审查效率，因为采用后项目对最终合并的PR进行审查、以及对最终关闭的PR进行解决的速度均有所加快。然而，Stale Bot也可能对贡献者产生负面影响，因为采用后项目的活跃贡献者数量显著下降。因此，仅依赖Stale Bot处理非活跃PR可能导致社区参与度降低，并增加贡献者流失的概率。