feat(docs): improve docs package

- use `src` instead of `unpackPhase`, this was a hangover from some previous logic
- execute usage generation hook against `treefmt` build instead of using `nix run`, as this would require recursive nix the build and is just more appropriate to use the built `treefmt`

Signed-off-by: Brian McGee <[email protected]>

Author: brianmcgee

docs/hooks.py

@@ -4,7 +4,7 @@
 def on_pre_build(**kwargs):
     with Path("./snippets/usage.txt").open("w") as f:
         subprocess.run(
-            ["nix", "run", ".#treefmt", "--", "--help"],
+            ["treefmt", "--help"],
             stdout=f,
             check=True,
         )

nix/packages/docs.nix

@@ -6,13 +6,13 @@
 pkgs.stdenvNoCC.mkDerivation {
   name = "docs";
 
-  unpackPhase = ''
-    cp -r ${../../docs}/* .
-    ls -alr
-  '';
+  src = ../../.;
 
   nativeBuildInputs =
-    (with pkgs.python3Packages; [
+    [
+      perSystem.self.treefmt
+    ]
+    ++ (with pkgs.python3Packages; [
       mike
       mkdocs
       mkdocs-material
@@ -33,6 +33,7 @@ pkgs.stdenvNoCC.mkDerivation {
     ];
 
   buildPhase = ''
+    cd docs
     mkdocs build
   '';