pin nixpkgs

nixpkgs-update

@@ -0,0 +1,30 @@
+#!/usr/bin/env nix-shell
+#!nix-shell -i bash -p bash curl jq
+#
+# Updates the pinned nixpkgs version
+set -euo pipefail
+
+source=nixpkgs.nix
+owner=NixOS
+repo=nixpkgs-channels
+branch=nixos-unstable
+
+echo "finding new revision for $owner/$repo@$branch..."
+
+rev=$(curl -sfL https://api.github.com/repos/$owner/$repo/git/refs/heads/$branch | jq -r .object.sha)
+
+echo "rev=$rev"
+
+url=https://github.com/$owner/$repo/archive/$rev.tar.gz
+
+echo "finding unpacked sha256 for $url..."
+
+sha256=$(nix-prefetch-url --unpack "$url")
+
+echo "generating new $source..."
+cat <<NEW_SOURCE | tee "$source"
+builtins.fetchTarball {
+  url = "$url";
+  sha256 = "$sha256";
+}
+NEW_SOURCE

nixpkgs.nix

@@ -0,0 +1,4 @@
+builtins.fetchTarball {
+  url = "https://github.com/NixOS/nixpkgs-channels/archive/4557b9f1f50aa813ae673fe6fcd30ca872968947.tar.gz";
+  sha256 = "0cam48cn042axcik9vqxsqjc2hwyb2grjbjxacsn4w0y1zk6k6l2";
+}

shell.nix

@@ -1,8 +1,10 @@
 let
+  nixpkgs = import ./nixpkgs.nix;
 
-  channelUrl = "https://github.com/NixOS/nixpkgs-channels/archive/nixos-unstable.tar.gz";
-  nixpkgs = builtins.fetchTarball channelUrl;
-  pkgs = import nixpkgs {};
+  pkgs = import nixpkgs {
+    config = {};
+    overlays = [];
+  };
 
 in pkgs.mkShell {