"You must type a file name" error thrown, when I create a .gitignore file on Windows

I arrive a little late but will give you the trick!! 😉

In the File Explorer, call your file .gitignore. and it will remove the ending '.'

A strange behavior from the file explorer but, hey!, it works 😅

Or create it from a text editor...

Windows Explorer doesn't allow you to create files that consist essentially of a file extension only. This is because Windows Explorer has the option to hide file extensions, leaving you with a file you cannot see (see Why doesn’t Explorer let you create a file whose name begins with a dot?). This is not a restriction of Windows itself, or the file system in use, though.

To create a file named .gitignore, you will have to use another tool to create it. A common solution is to create a text file (e.g. test.txt), open it in Notepad, and select Save As... to rename the file to .gitignore.

The Windows command interpreter also allows you to create files without imposing the additional restrictions of Windows Explorer. A more direct solution would then be to create the file from the command line. This can be done using the following command:

copy NUL .gitignore

in cmd,just type

 echo. 2>.name_you_want

or

. 2>.name_you_want

to create file.

if creating a dir,just type

mkdir .folder_name_you_want

Use command line instead.
I was also having the same error. The problem was . at the start of file or folder name.
So I created it by command line.