Social media, especially Twitter, has always been a part of the professional lives of software developers, with prior work reporting on a diversity of usage scenarios, including sharing information, staying current, and promoting one’s work. However, previous studies of Twitter use by software developers are generally restricted to surveys or small samples, and typically lack information about activities of the study subjects (and their outcomes) on other platforms. To enable such future research, in this paper we propose a computational approach to cross-linking users on Twitter and GitHub, the dominant platform for hosting open-source development, revealing 70,428 users active on both. As a preliminary analysis of this dataset, we report on a case study of 800 tweets by open-source developers about GitHub work, combining precise automatic characterization of tweet authors in terms of their relationship to the GitHub items linked in their tweets with a deep qualitative analysis of the tweet contents. We find that developers have very distinct behavioral patterns when including GitHub links in their tweets and these patterns are correlated with the relationship between the tweet author and the repository they link to. Based on this analysis, we hypothesize about what might explain such behavioral differences and what the implications of different tweeting patterns could be for the sustainability of GitHub projects.