add programs.man module

Note: this doesn't add man to systemPackages by default,
only man-old builds on darwin and the system version works fine.

default.nix

@@ -44,6 +44,7 @@ let
         ./modules/services/nix-gc.nix
         ./modules/programs/bash.nix
         ./modules/programs/fish.nix
+        ./modules/programs/man.nix
         ./modules/programs/nix-script.nix
         ./modules/programs/tmux.nix
         ./modules/programs/vim.nix

modules/environment/default.nix

@@ -51,7 +51,7 @@ in {
 
     environment.extraOutputsToInstall = mkOption {
       type = types.listOf types.str;
-      default = [ "man" ];
+      default = [];
       example = [ "doc" "info" "devdoc" ];
       description = "List of additional package outputs to be symlinked into <filename>/run/current-system/sw</filename>.";
     };

modules/programs/man.nix

@@ -0,0 +1,27 @@
+{ config, lib, pkgs, ... }:
+
+with lib;
+
+{
+  options = {
+
+    programs.man.enable = mkOption {
+      type = types.bool;
+      default = true;
+      description = ''
+        Whether to enable manual pages and the <command>man</command> command.
+        This also includes "man" outputs of all <literal>systemPackages</literal>.
+      '';
+    };
+
+  };
+
+
+  config = mkIf config.programs.man.enable {
+
+    environment.pathsToLink = [ "/share/man" ];
+
+    environment.extraOutputsToInstall = [ "man" ];
+
+  };
+}