Nixpkgs is a collection of packages for the [Nix](https://nixos.org/nix/) package manager. It is periodically build and tested by the [hydra](http://hydra.nixos.org/) build daemon as so-called channels. To get channel information via git, add [nixpkgs-channels](https://github.com/NixOS/nixpkgs-channels.git) as a remote `git remote add nixpkgs-channels https://github.com/NixOS/nixpkgs-channels.git`. It is recommended to maintain custom changes on top of the `nixos-unstable` branch of `nixpkgs-channels`. For pull-requests, please rebase onto nixpkgs master.