There is a project with .gitignore in root folder:

*
!.gitignore

I need to add new folder to the project:

/new_folder/file_1
/new_folder/file_2
/new_folder/subfolder/file_3

So I added to .gitignore a line at the end:

*
!.gitignore
!new_folder

But Git is not seeing this new_folder as if it does not exist.