During a group project at university, we needed to develop a web application. We were seven on the project and there was a lot of work to do. Thus, we decided to split the amount of work between the members. In order to share our code in the group we used a specific software called Source Tree.
People were updating the general code branch when they finished their own code by adding it.
But we faced a problem: the general code was never the same and errors appeared when different parts were merged.
We discovered that this problem came from the fact that people were changing the general code at the same time. Thus, we established a rule, before modifying the general code, the person had to warn the group she is remoting the code and then let them now when it is over. And this allow us to have a common code without errors.