Pull Request Governance In Open Source Communities

Pull requests facilitate inclusion and improvement of contributions in distributed software projects, especially in open source communities. An author makes a pull request to present a contribution as a candidate for inclusion in a code base. The request is inspected by maintainers and reviewers. The initiated process of review and collaborative improvement can be loaded with debates, opinions, and emotions. It heavily influences the atmosphere in the community. It can demotivate and detract contributors or it can fail to guard the code quality. Both problems put the existence of a community at risk. This mixed methods study aims to elucidate the mechanisms of evaluating pull requests in diverse open source software communities from the perspectives of developers and maintainers. We interviewed 30 participants from five different communities and conducted a survey with N=387 respondents. The data shows that acceptance of contributions in open source depends not only on technical criteria, but also significantly on social and strategic aspects. As a result, we identify three governance styles for pull requests: (1) protective, (2) equitable, and (3) lenient. While the protective style values trustworthiness and reliability of the contributor, the lenient style believes in creating a positive and welcoming environment where contributors are mentored to evolve contributions until the community standards are met. Each of the governance styles safeguards the quality of the project code in different ways. We hope that this material will help researchers and community managers to obtain a more nuanced view on the peculiarities of different communities and the strengths and weakness of their pull requests evaluation process.