CLIONE: Clone Modification Support for Pull Request Based Development

A code clone (clone) is known as one of the factors that makes software maintenance difficult. Thus, in software maintenance, clone modification is essential. An existing study proposed a tool that notifies developers of information about clone changes so that the developers can modify clones efficiently. However, the existing tool is premised on regular execution and not designed to be triggered by external factors except for time. Hence, the existing tool is difficult to be executed triggered by development workflow, such as modifying source code or merging branches, and we think this causes some issues. Consequently, in this study, we propose a new clone modification support technique aimed to integrate into pull request (PR) based development for solving those issues. The proposed technique detects code fragments that need modifications by tracking clones at the time of creating PRs. Moreover, we made three improvements for more accurate clone change tracking. Additionally, we implemented the proposed technique as a software tool, CLIONE. To evaluate CLIONE, we investigated the proportion of PRs in which clones have been modified non-simultaneously, and also we compared the results of clone change tracking with the existing tool. As a result, 11.9%~30.4% of PRs included non-simultaneously modified clones, and we confirmed that CLIONE was able to track clone changes more accurately than the existing tool. CLIONE is available at https://github.com/T45K/CLIONE.