This tool is used to update the Haskell package set in
nixpkgs
(hackage-packages.nix).
It gets used by the
maintainers/scripts/haskell/regenerate-hackage-packages.sh
script in nixpkgs. There are usually no reasons to run this tool any other way.
For development and testing you can modify the environment variable HACKAGE2NIX
of that script.
Further informations regarding the usage of hackage2nix in nixpkgs can be found under nixpkgs:pkgs/development/haskell-modules/HACKING.md.
This must be run on a case sensitive file system.
On OSX you can use this to create one
(you can replace 60g with 4g as that should be plenty).
For building cabal2nix and hackage2nix you need to have cabal-install
installed.
For development setup see the toplevel cabal2nix README.
There is a now out-dated video on YouTube that gives a thorough walk-through of the previous work flow. It also explains many of the background considerations.