Many teams are working with Visual Studio Online (VSO), a hosted Team Foundation Server that provides source control and issue tracking as a cloud service. While VSO comes with a build server as well, lots of developers prefer to use TeamCity for their continuous integration story because of its advanced features to automatically run builds for feature branches,  automatic merge and many others. TeamCity supports building projects that are hosted on Visual Studio Online, the only thing we have to do is add a VCS root to our build configurations. Depending on the version control system used