Understanding the Helpfulness of Stale Bot for Pull-based Development:
  An Empirical Study of 20 Large Open-Source Projects
SayedHassan Khatoonabadi Diego Elias Costa Suhaib Mujahid Emad Shihab
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.