Version control systems such as Git support parallel collaborative work and became very widespread in the open-source community. While Git ooers some very interesting features, resolving collaborative connicts that arise during synchronization of parallel changes is a time-consuming task. In this paper we present an analysis of concurrency and connicts in oocial Git repository of four projects: Rails, IkiWiki, Samba and Linux Kernel. We also analyze how ooen users decide to rollback to previous document version when the integration process results in connict. Finally, we discuss the mechanism adopted by Git to consider changes made on two continuous lines as conflicting.