nix: rename custom -> packages

nix/packages/nd/default.nix

@@ -0,0 +1,15 @@
+{
+  writeShellApplication,
+
+  nix-output-monitor,
+  nvd,
+}:
+
+writeShellApplication {
+  name = "nd";
+  runtimeInputs = [
+    nix-output-monitor
+    nvd
+  ];
+  text = builtins.readFile ./nd.sh;
+}

nix/packages/nd/nd.sh

@@ -0,0 +1,52 @@
+bold=$(tput bold)
+normal=$(tput sgr0)
+
+while [ $# -gt 0 ]; do
+	case "$1" in
+	--clean*)
+		shopt -s nullglob
+		for link in nix-diff*; do
+			set -x
+			unlink "$link"
+			set +x
+		done
+		exit 0
+		;;
+	--last*)
+		if [[ "$1" != *=* ]]; then shift; fi
+		_last_hash="${1#*=}"
+		;;
+	--hostname*)
+		if [[ "$1" != *=* ]]; then shift; fi
+		_hostname="${1#*=}"
+		;;
+	*)
+		printf "Error: unknown argument"
+		exit 1
+		;;
+	esac
+	shift
+done
+
+echo "Comparing ${bold}$_hostname${normal}'s configuration of ${bold}HEAD${normal} and ${bold}$_last_hash${normal}"
+
+last_ref=".?ref=${_last_hash}#nixosConfigurations.${_hostname}.config.system.build.toplevel"
+last_link="nix-diff-${_last_hash:0:7}"
+if [ -L "$last_link" ]; then
+	echo "Found link ${bold}$last_link${normal}"
+else
+	echo "Starting configuration build at ${bold}$_last_hash${normal}"
+	nix build "$last_ref" --out-link "$last_link" >/dev/null 2>&1 &
+fi
+
+echo "Starting configuration build at ${bold}HEAD${normal}"
+this_ref=".#nixosConfigurations.${_hostname}.config.system.build.toplevel"
+this_link="nix-diff-HEAD"
+nix build "$this_ref" --out-link "$this_link" --log-format internal-json --verbose |& nom --json
+
+echo "Waiting for all builds to complete..."
+wait
+echo "Completed."
+
+echo "Diffing..."
+nvd diff "$last_link" "$this_link"