niv/nix/packages.nix

{ writeText
, runCommand
, lib
, snack-lib
}:
rec
{ niv = snack-lib.executable ../package.yaml;
  readme = writeText "README.md"
    (with
      { template = builtins.readFile ../README.tpl.md;
        niv_help = builtins.readFile
          (runCommand "niv_help" { buildInputs = [ niv ]; }
            "niv --help > $out"
          );
        niv_cmd_help = cmd: builtins.readFile
          (runCommand "niv_${cmd}_help" { buildInputs = [ niv ]; }
            "niv ${cmd} --help > $out"
          );
        cmds = [ "add" "update" "drop" "init" "show" ];
      };
    lib.replaceStrings
      ([ "replace_niv_help" ] ++ (map (cmd: "replace_niv_${cmd}_help") cmds))
      ([ niv_help ] ++ (map niv_cmd_help cmds))
      template
    );
  readme-test = runCommand "README-test" {}
    "diff ${../README.md} ${readme} && echo dummy > $out";
}