(No) Influence of Continuous Integration on the Commit Activity in GitHub Projects — Supplementary Material

A core goal of Continuous Integration (CI) is to make small incremental changes to software projects. Those changes should then be frequently integrated into a mainline repository or branch. Our paper presents an empirical study investigating if developers adjust their commit activity towards this goal after projects introduce CI. To this end, we analyzed the commit and merge activity in 93 GitHub projects that introduced the hosted CI system Travis CI and have been developed on GitHub for at least one year before the introduction. With our analysis, we only found one non-negligible effect, i.e. an increased merge ratio, meaning that there are more merging commits in relation to all commits after the projects started using Travis CI. However, we observed the same effect in a random sample of GitHub projects—the effect is likely to be caused by the growing adoption of the pull-based software development model.