An Empirical Analysis of Git Commit Logs for Potential Inconsistency in Code Clones

TL;DR

This study analyzes git commit logs of code clone pairs across 45 Apache repositories, revealing infrequent changes, partial co-change, and a significant portion of potentially inconsistent clone pairs, highlighting the need for better clone management.

Contribution

It provides an empirical analysis of commit logs for code clone pairs, revealing patterns of change frequency, co-change ratio, and potential inconsistencies, which were previously underexplored.

Findings

Clone snippets are infrequently changed, typically 2-3 times.

About 50% of clone changes are co-changed, with 10-20% potentially inconsistent.

35-65% of clone pairs are potentially inconsistent, indicating a need for better management.

Abstract

Code clones are code snippets that are identical or similar to other snippets within the same or different files. They are often created through copy-and-paste practices and modified during development and maintenance activities. Since a pair of code clones, known as a clone pair, has a possible logical coupling between them, it is expected that changes to each snippet are made simultaneously (co-changed) and consistently. There is extensive research on code clones, including studies related to the co-change of clones; however, detailed analysis of commit logs for code clone pairs has been limited. In this paper, we investigate the commit logs of code snippets from clone pairs, using the git-log command to extract changes to cloned code snippets. We analyzed 45 repositories owned by the Apache Software Foundation on GitHub and addressed three research questions regarding commit frequency, co-change ratio, and commit patterns. Our findings indicate that (1) on average, clone snippets are changed infrequently, typically only two or three times throughout their lifetime, (2) the ratio of co-changes is about half of all clone changes, with 10-20\% of co-changed commits being concerning (potentially inconsistent), and (3) 35-65\% of all clone pairs being classified as concerning clone pairs (potentially inconsistent clone pairs). These results suggest the need for a consistent management system through the commit timeline of clones.