Untangling Fine-Grained Code Changes

TL;DR

This paper introduces a new dataset and a tool called EpiceaUntangler that helps developers automatically untangle and create atomic commits from tangled code changes, improving code review and project analysis.

Contribution

It provides the first publicly available dataset of manually untangled code changes and presents a novel approach, EpiceaUntangler, for automatic untangling using fine-grained change information.

Findings

Median success rate of 91% in automatic untangling

Average success rate of 75% in real-world deployment

Effective assistance for developers in creating atomic commits

Abstract

After working for some time, developers commit their code changes to a version control system. When doing so, they often bundle unrelated changes (e.g., bug fix and refactoring) in a single commit, thus creating a so-called tangled commit. Sharing tangled commits is problematic because it makes review, reversion, and integration of these commits harder and historical analyses of the project less reliable. Researchers have worked at untangling existing commits, i.e., finding which part of a commit relates to which task. In this paper, we contribute to this line of work in two ways: (1) A publicly available dataset of untangled code changes, created with the help of two developers who accurately split their code changes into self contained tasks over a period of four months; (2) a novel approach, EpiceaUntangler, to help developers share untangled commits (aka. atomic commits) by using fine-grained code change information. EpiceaUntangler is based and tested on the publicly available dataset, and further evaluated by deploying it to 7 developers, who used it for 2 weeks. We recorded a median success rate of 91% and average one of 75%, in automatically creating clusters of untangled fine-grained code changes.