Improve detect NixOS version

[Izorkin]

Description

Improve detect NixOS version

Before PR:

neofetch --off --distro_shorthand on | grep OS
OS: nixos 22.11 x86_64

neofetch --off --distro_shorthand tiny | grep OS
OS: nixos x86_64

neofetch --off --distro_shorthand off | grep OS
OS: NixOS 22.11 (Raccoon) x86_64

After PR:

neofetch --off --distro_shorthand on | grep OS
OS: NixOS 22.11 (Raccoon) x86_64

neofetch --off --distro_shorthand tiny | grep OS
OS: NixOS x86_64

neofetch --off --distro_shorthand off | grep OS
OS: NixOS 22.11.git.31109649164 (Raccoon) x86_64

[hykilpikonna]

It looks kind of long but anyways... thanks!

[hykilpikonna]

Thank you for your contribution!

This PR is merged into hyfetch since this repo (dylanaraps/neofetch) seems no longer maintained.

HyFetch is a fork of neofetch with LGBTQ pride flags, but the repo also serves as an updated version of neofetch, addressing many pull requests that are not merged in the original repo.

[Izorkin]

Neofetch does not display the OS build revision separately, so I suggested this variant.

The short version can be displayed with the following command:

neofetch --distro_shorthand on
...
OS: NixOS 22.11 (Raccoon) x86_64
...