Visualizing a Tangled Change for Supporting Its Decomposition and Commit Construction

Developers often save multiple kinds of source code edits into a commit in a version control system, producing a tangled change, which is difficult to understand and revert. However, its separation using an existing sequence-based change representation is tough. We propose a new visualization technique to show the details of a tangled change and align its component edits in a tree structure for expressing multiple groups of changes. Our technique is combined with utilizing refactoring detection and change relevance calculation techniques for constructing the structural tree. Our combination allows us to divide the change into several associations. We have implemented a tool and conducted a controlled experiment with industrial developers to confirm its usefulness and efficiency. Results show that by using our tool with tree visualization, the subjects could understand and decompose tangled changes easier, faster, and higher accuracy than the baseline file list visualization.