A Study on Evolution of Pull Request Template: How Are Pull Request Initial Contents Organised and Evolved?

Pull request templates are used to reduce inconsistencies in information included in submitted pull requests in GitHub. A few studies have explored the effectiveness of employing pull request template. However, there is still a lack of how to evolve PR templates during software development. Knowledge is crucial to efficiently manage PR templates. To address this gap, we conducted a study on the organisation and evolution of pull request template initial content. For the study, 2689 target PR template files from 2614 public GitHub repositories were collected and 7 PR content categories including Description, Checklist, Reference, Test, Type, Additional Info, and Other were manually defined from the target files. Based on the defined categories, a pull request content classifier was built. By using the target dataset and the classifier, initial content organisation and its evolution were investigated. The results showed that 68% of target pull request templates organise their initial content with only two or fewer categories, and the initial content organisation remains in 71% of the entire pull request templates.