An Empirical Study on Inter-Commit Times in SVN

Until now, centralized revision control systems such as Subversion (SVN) have been widely used in open-source software (OSS) development. Commit is a basic and important operation for revision control, and it has attracted the attention of a large number of researchers. As far as we know, few of prior studies investigated the distribution of inter-commit times (known as commit intervals), which reveals the development dynamics of an OSS project to some extent. To gain a better understanding on OSS development processes, we conducted an empirical study on two representative projects written in Java, and found that (1) the distributions of commit intervals in the two projects in question roughly follow power laws, with commit bursts (i.e., the revisions in a SVN repository are updated quickly over a period of time) and heavy tails, and (2) the working mode of SVN and (full-time or volunteer) developers’ work habits contribute to commit bursts, while active committer’s individual behavior (such as his/her tasks completion and illness) and long vacations are the primary factors that result in long inter-commit times. The findings could provide a new insight into schedule planning for OSS projects based on developers’ historical commit behavior. Keywords-subversion; development dynamics; commit interval; burst; heavy tail