Initialize Git repositories
To start controlling a project directory that is currently not under version control, go to Tools > Git, and then select Create Repository.
Qt Creator creates a new subdirectory named .git that has all the necessary repository files. Qt Creator also creates a file named .gitignore that contains patterns of files that should not be tracked by Git (such as build directories).
Git does not track anything in the project yet, so you need to create an initial commit to start tracking the project files.
See also How to: Use Git and Using Git.