(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, which are integrated frequently into a mainline repository or branch. Our paper presents an empirical study that investigates if developers adjust their commit activity towards the above-mentioned goal after projects start using CI. We analyzed the commit and merge activity in 93 GitHub projects that introduced the hosted CI system Travis CI, but have also been developed on GitHub for at least one year before introducing CI. In our analysis, we only found one non-negligible effect, an increased merge ratio, meaning that there were more merging commits in relation to all commits after the projects started using Travis CI. This effect has also been reported in related work. 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 instead of the introduction of CI.