extremely hacky first pass at autogenerated module docs

doc/extract-options.nix

@@ -0,0 +1,55 @@
+let
+  overlay = import ../overlay.nix;
+  pkgs = import <nixpkgs> ( {
+    overlays = [overlay];
+    config = {
+      allowUnsupportedSystem = true; # mipsel
+      permittedInsecurePackages = [
+        "python-2.7.18.6"       # kernel backports needs python <3
+      ];
+    };
+  });
+  inherit (pkgs) lib;
+  inherit (lib) types;
+  modulenames =
+    builtins.attrNames
+      (lib.filterAttrsRecursive
+        (n: t:
+          (t=="directory") ||
+          ((t=="regular") && ((builtins.match ".*\\.nix$" n) != null)))
+        (builtins.readDir ../modules));
+  modulefiles = builtins.map (n: builtins.toPath "${../modules}/${n}") modulenames;
+  eval = (lib.evalModules {
+    modules = [
+      { _module.args = { inherit pkgs; lib = pkgs.lib; }; }
+    ] ++ modulefiles;
+  });
+  conf = eval.config;
+  optToDoc = name: opt : {
+    inherit name;
+    description = opt.description or null;
+    default = opt.default or null;
+    visible =
+      if (opt ? visible && opt.visible == "shallow")
+      then true
+      else opt.visible or true;
+    readOnly = opt.readOnly or false;
+    type = opt.type.description or "unspecified";
+  };
+  spliceServiceDefn = item :
+    if item.type == "parametrisable s6-rc service definition"
+    then
+      let sd = lib.attrByPath item.loc ["not found"] conf;
+      in item // {
+        parameters =
+          let x = lib.mapAttrsToList optToDoc sd.parameters; in x;
+      }
+    else
+      item;
+  o = builtins.map spliceServiceDefn
+    (pkgs.lib.optionAttrSetToDocList eval.options);
+in {
+  doc = pkgs.writeText "options.json"
+    (builtins.unsafeDiscardStringContext (builtins.toJSON o))
+  ;
+}