rename is missing

[cainrus]

fs api: https://nodejs.org/api/fs.html#fs_fs_rename_oldpath_newpath_callback

[Viijay-Kr]

@cainrus Is there a potential use case for rename in MemoryFileSystem?

[cainrus]

I had tried to mock real fs package with memory-fs to boost performance of multiple packages and stumbled upon the problem (missing rename). I don't know is it a problem for other users, but i thought that memory-fs will try to repeat fs API.