diff --git a/Makefile b/Makefile
index e45c766..b002431 100644
--- a/Makefile
+++ b/Makefile
@@ -11,3 +11,8 @@ docs-build:
 .PHONY: update
 update:
 	npins update
+
+# Ideally this should be done before committing.
+.PHONY: format
+format:
+	treefmt
diff --git a/shell.nix b/shell.nix
index d1cff49..c471c34 100644
--- a/shell.nix
+++ b/shell.nix
@@ -4,19 +4,16 @@ in
 { pkgs ? import sources.nixos-unstable { } }:
 
 let
-  websiteDevshell = import ./docs/shell.nix { inherit pkgs; };
+  websitePkg = import ./docs { inherit pkgs; };
 in
 pkgs.mkShell {
-  packages = with pkgs; [
-    websiteDevshell
+  inputsFrom = [ websitePkg ];
 
+  packages = with pkgs; [
     npins
     treefmt
     nixpkgs-fmt
 
-    hugo
-    asciidoctor
-
     # For easy validation of the test suite.
     yajsv
     jq
diff --git a/treefmt.toml b/treefmt.toml
new file mode 100644
index 0000000..4deb3fd
--- /dev/null
+++ b/treefmt.toml
@@ -0,0 +1,8 @@
+[global]
+excludes = [
+  "npins/default.nix"
+]
+
+[formatter.nix]
+command = "nixfmt"
+includes = [ "*.nix" ]