modules/docs: add CONTRIBUTING page

Author: MattSturgeon

modules/docs/default.nix

@@ -1,4 +1,30 @@
-{ lib, ... }:
+{ lib, pkgs, ... }:
+let
+  # Replaces absolute links to the docs with relative links
+  # FIXME: use pandoc filters to do this with an AST
+  fixLinks =
+    name: src:
+    pkgs.runCommand name
+      {
+        inherit src;
+        github = "https://github.com/nix-community/nixvim/blob/main/";
+        baseurl = "https://nix-community.github.io/nixvim/";
+      }
+      ''
+
+        cp $src $out
+
+        # replace relative links with links to github
+        # TODO: it'd be nice to match relative links without a leading ./
+        # but that is less trivial
+        substituteInPlace $out --replace-quiet "./" "$github"
+
+        # replace absolute links
+        substituteInPlace $out --replace-quiet "$baseurl" "./"
+
+        # TODO: replace .html with .md
+      '';
+in
 {
   options.enableMan = lib.mkOption {
     type = lib.types.bool;
@@ -16,8 +42,24 @@
     ./platforms.nix
   ];
 
-  config.docs.optionPages = {
-    docs = {
+  config.docs = {
+    pages."" = {
+      menu.section = "header";
+      menu.location = [ "Home" ];
+      source =
+        let
+          src = pkgs.callPackage ./readme.nix {
+            # TODO: get `availableVersions` and `baseHref` from module options
+          };
+        in
+        fixLinks src.name src;
+    };
+    pages.contributing = {
+      menu.section = "footer";
+      menu.location = [ "Contributing" ];
+      source = fixLinks "contributing" ../../CONTRIBUTING.md;
+    };
+    optionPages.docs = {
       optionScopes = [ "docs" ];
       page.menu.location = [ "docs" ];
       page.text = ''

modules/docs/readme.nix

@@ -21,15 +21,11 @@ runCommand "index.md"
         {
           start = "<!-- START DOCS -->";
           end = "<!-- STOP DOCS -->";
-          baseurl = "https://nix-community.github.io/nixvim/";
           src = ../../README.md;
         }
         ''
           # extract relevant section of the README
           sed -n "/$start/,/$end/p" $src > $out
-          # replace absolute links
-          substituteInPlace $out --replace-quiet "$baseurl" "./"
-          # TODO: replace .html with .md
         '';
 
     docs_versions =