For teams using distributed version control systems, the right collaborative development workflows can help maintaining the long-term quality of project repositories and improving work efficiency. Despite the fact that the workflows are important, empirical evidence on how they are used and what impact they make on the project repositories is scarce. Most suggestions on the use of workflows are merely expert opinions. Often, there is only some anecdotal evidence that underpins those advices. As a result, we do not know what workflows are used, how the developers are using them, and what impact do they have on the project repositories. This work investigates the various collaborative development workflows in eight major open-source projects, identifies and analyses the workflows together with the structures of their project repositories, discusses their similarities and differences, and lays out the future works.