man: add module

modules/default.nix

@@ -31,6 +31,7 @@ let
     ./programs/htop.nix
     ./programs/info.nix
     ./programs/lesspipe.nix
+    ./programs/man.nix
     ./programs/rofi.nix
     ./programs/ssh.nix
     ./programs/termite.nix

modules/misc/news.nix

@@ -328,6 +328,16 @@ in
           will be set only on zsh launch.
         '';
       }
+
+      {
+        time = "2017-10-15T13:59:47+00:00";
+        message = ''
+          A new module is available: 'programs.man'.
+
+          This module is enabled by default and makes sure that manual
+          pages are installed for packages in 'home.packages'.
+        '';
+      }
     ];
   };
 }

modules/programs/man.nix

@@ -0,0 +1,22 @@
+{ 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>home.packages</literal>.
+      '';
+    };
+  };
+
+  config = mkIf config.programs.man.enable {
+    home.packages = [ pkgs.man-db ];
+    home.extraOutputsToInstall = [ "man" ];
+  };
+}