There are file and directory names which are legal in Git and most operating systems but illegal in Windows. They should be avoided in case a developer happens to use Windows.

The following names are illegal as bare names as well as with extensions regardless of case for files or directories. For instance CoM6, cOm6.txt, com6.foo.jpg, etc are all illegal. Windows will refuse to create those files if you try to check them out.

From: https://docs.microsoft.com/en-us/windows/win32/fileio/naming-a-file

Do not use the following reserved names for the name of a file:

CON, PRN, AUX, NUL, COM1, COM2, COM3, COM4, COM5, COM6, COM7, COM8, COM9, LPT1, LPT2, LPT3, LPT4, LPT5, LPT6, LPT7, LPT8, and LPT9. Also avoid these names followed immediately by an extension; for example, NUL.txt is not recommended. For more information, see Namespaces.