@@ -0,0 +1,15 @@
+{
+  "version": "1",
+  "sources": {
+    "nixpkgs": {
+      "type": "GitHub",
+      "fetchType": "tarball",
+      "owner": "nixos",
+      "repo": "nixpkgs",
+      "branch": "nixpkgs-unstable",
+      "revision": "d233902339c02a9c334e7e593de68855ad26c4cb",
+      "url": "https://github.com/nixos/nixpkgs/archive/d233902339c02a9c334e7e593de68855ad26c4cb.tar.gz",
+      "hash": "sha256-30sZNZoA1cqF5JNO9fVX+wgiQYjB7HJqqJ4ztCDeBZE="
+    }
+  }
+}

@@ -0,0 +1,53 @@
+# Generated by lon. Do not modify!
+let
+
+  lock = builtins.fromJSON (builtins.readFile ./lon.lock);
+
+  # Override with a path defined in an environment variable. If no variable is
+  # set, the original path is used.
+  overrideFromEnv =
+    name: path:
+    let
+      replacement = builtins.getEnv "LON_OVERRIDE_${name}";
+    in
+    if replacement == "" then
+      path
+    else
+    # this turns the string into an actual Nix path (for both absolute and
+    # relative paths)
+    if builtins.substring 0 1 replacement == "/" then
+      /. + replacement
+    else
+      /. + builtins.getEnv "PWD" + "/${replacement}";
+
+  fetchSource =
+    args@{ fetchType, ... }:
+    if fetchType == "git" then
+      builtins.fetchGit (
+        {
+          url = args.url;
+          ref = args.branch;
+          rev = args.revision;
+          narHash = args.hash;
+          submodules = args.submodules;
+        }
+        // (
+          if args ? lastModified then
+            {
+              inherit (args) lastModified;
+              shallow = true;
+            }
+          else
+            { }
+        )
+      )
+    else if fetchType == "tarball" then
+      builtins.fetchTarball {
+        url = args.url;
+        sha256 = args.hash;
+      }
+    else
+      builtins.throw "Unsupported source type ${fetchType}";
+
+in
+builtins.mapAttrs (name: args: overrideFromEnv name (fetchSource args)) lock.sources

@@ -1,5 +1,11 @@
 {
-  pkgs ? (import <nixpkgs> { }),
+  pkgs ? (
+    let
+      sources = import ./lon.nix;
+      pkgs = import sources.nixpkgs { };
+    in
+    pkgs
+  ),
   lib ? pkgs.lib,
 }:
 let
@@ -19,6 +25,7 @@ '';
 in
 pkgs.mkShellNoCC {
   packages = with pkgs; [
+    lon
     dnscontrol
     prettier