nixos-mailserver/nix/sources.json

{
    "nixpkgs-unstable": {
        "branch": "nixos-unstable",
        "description": "A read-only mirror of NixOS/nixpkgs tracking the released channels. Send issues and PRs to",
        "homepage": "https://github.com/NixOS/nixpkgs",
        "owner": "NixOS",
        "repo": "nixpkgs-channels",
        "rev": "84d74ae9c9cbed73274b8e4e00be14688ffc93fe",
        "sha256": "0ww70kl08rpcsxb9xdx8m48vz41dpss4hh3vvsmswll35l158x0v",
        "type": "tarball",
        "url": "https://github.com/NixOS/nixpkgs-channels/archive/84d74ae9c9cbed73274b8e4e00be14688ffc93fe.tar.gz",
        "url_template": "https://github.com/<owner>/<repo>/archive/<rev>.tar.gz"
    }
}