To quote the XDG specification:
There is a single base directory relative to which user-specific
data files should be written. This directory is defined by the\
environment variable $XDG_DATA_HOME.
Rather than adding another directory to $HOME, I think that it's better
to follow this standard to avoid a cluttered home-dir.
*** NixOS *** NixOS is a Linux distribution based on the purely functional package management system Nix. More information can be found at http://nixos.org/nixos and in the manual in doc/manual.