Lean software development methods focused on collaboration and interaction with fast and smaller deployment cycles.
Git is an excellent tool for an Agile team considering that it allows decentralized and simultaneous development.
Branching in an Agile environment usually happens around user stories with one or more developers working on it.
If more than one developer then another branch for each developer is also used with their initials, and US id.
After its tested merge into master and remove the branch.
Tools like GitLab enhance collaboration by adding dialog around code mainly through issues and merge requests.