When using Git Winch you need to create a new file from here, instead of from within any application. Only then will Git Winch would become aware of which files are created. There is a special folder named templates in the same folder where you installed the Git Winch application. If you keep a file of a particular extension in that folder, then that file will be used as a template when you create a new file.
If such a template file is not available for a particular extension, then Git Winch will create a zero-byte file for it. Such zero-byte files may not be acceptable by certain applications.
Using templates is a very useful feature. Explained more here.