How Much Do Code Repositories Include Peripheral Modifications?

In the last decade, a variety of studies on mining software repositories has been conducted. Mining repositories has a potential to obtain useful knowledge for the future development and maintenance. When software repositories are mined, large commits in them are often excluded from mining targets because large commits include merging and we believe that large commits include peripheral modifications, which may affect negative impacts on mining code repositories. However, if large commits include code modifications, excluding large commits loses such modifications unintentionally. Moreover, such data cleansing assumes that there are no peripheral modifications in small commits. In this paper, we investigate how much peripheral modifications are included in commits in code repositories. As a result, we found that excluding large commits is insufficient to remove hindrances in commits for mining code repositories.