GitHub Actions was introduced in 2019 and constitutes an integrated alternative to CI/CD services for GitHub repositories. The deep integration with GitHub allows repositories to easily automate software development workflows. This paper empirically studies the use of GitHub Actions on a dataset comprising 68K repositories on GitHub, of which 43.9% are using GitHub Actions workflows. We analyse which workflows are automated and identify the most frequent automation practices. We show that reuse of actions is a common practice, even if this reuse is concentrated in a limited number of actions. We study which actions are most frequently used and how workflows refer to them. Furthermore, we discuss the related security and versioning aspects. As such, we provide an overview of the use of GitHub Actions, constituting a necessary first step towards a better understanding of this emerging ecosystem and its implications on collaborative software development in the GitHub social coding platform.

Continuous integration (CI) services are used in collaborative open source projects to automate parts of the development workflow. Such services have been in widespread use for over a decade, with new CIs being introduced over the years, sometimes overtaking other CIs in popularity. We conducted a longitudinal empirical study over a period of nine years, aiming to better understand this rapidly evolving CI landscape. By analysing the development history of 91,810 GitHub repositories of active npm packages having used at least one CI service, we quantitatively studied the evolution of seven popular CIs, specifically focusing on their co-usage and migration in the considered repositories. We provide statistical evidence of the rise of GitHub Actions, that has become the dominant CI service in less than 18 months time. This coincides with the fall of Travis that has seen an important decrease in usage, likely due to a combination of policy changes and migrations to GitHub Actions.

Software package distributions form large dependency networks maintained by large communities of contributors. My PhD research will consist of analysing the evolution of the socio-technical congruence of these package dependency networks, and studying its impact on the health of the ecosystem and its community. I have started a longitudinal empirical study of Cargo's dependency network and the social (commenting) and technical (development) activities in Cargo's package repositories on GitHub, and present some preliminary findings.