treewide: make option descriptions constants

escape interpolations in descriptions where possible, replace them with
sufficiently descriptive text elsewhere. also expand cfg.* paths in
descriptions.

nixos/modules/services/games/terraria.nix

@@ -1,9 +1,10 @@
-{ config, lib, pkgs, ... }:
+{ config, lib, options, pkgs, ... }:
 
 with lib;
 
 let
   cfg   = config.services.terraria;
+  opt   = options.services.terraria;
   worldSizeMap = { small = 1; medium = 2; large = 3; };
   valFlag = name: val: optionalString (val != null) "-${name} \"${escape ["\\" "\""] (toString val)}\"";
   boolFlag = name: val: optionalString val "-${name}";
@@ -36,7 +37,7 @@ in
         type        = types.bool;
         default     = false;
         description = ''
-          If enabled, starts a Terraria server. The server can be connected to via <literal>tmux -S ${cfg.dataDir}/terraria.sock attach</literal>
+          If enabled, starts a Terraria server. The server can be connected to via <literal>tmux -S ''${config.${opt.dataDir}}/terraria.sock attach</literal>
           for administration by users who are a part of the <literal>terraria</literal> group (use <literal>C-b d</literal> shortcut to detach again).
         '';
       };

nixos/modules/services/misc/airsonic.nix

@@ -1,9 +1,10 @@
-{ config, lib, pkgs, ... }:
+{ config, lib, options, pkgs, ... }:
 
 with lib;
 
 let
   cfg = config.services.airsonic;
+  opt = options.services.airsonic;
 in {
   options = {
 
@@ -78,7 +79,7 @@ in {
         description = ''
           List of paths to transcoder executables that should be accessible
           from Airsonic. Symlinks will be created to each executable inside
-          ${cfg.home}/transcoders.
+          ''${config.${opt.home}}/transcoders.
         '';
       };
 

nixos/modules/services/misc/mediatomb.nix

@@ -277,13 +277,13 @@ in {
       user = mkOption {
         type = types.str;
         default = "mediatomb";
-        description = "User account under which ${name} runs.";
+        description = "User account under which the service runs.";
       };
 
       group = mkOption {
         type = types.str;
         default = "mediatomb";
-        description = "Group account under which ${name} runs.";
+        description = "Group account under which the service runs.";
       };
 
       port = mkOption {
@@ -340,7 +340,7 @@ in {
         type = types.bool;
         default = false;
         description = ''
-          Allow ${name} to create and use its own config file inside the <literal>dataDir</literal> as
+          Allow the service to create and use its own config file inside the <literal>dataDir</literal> as
           configured by <option>services.mediatomb.dataDir</option>.
           Deactivated by default, the service then runs with the configuration generated from this module.
           Otherwise, when enabled, no service configuration is generated. Gerbera/Mediatomb then starts using

nixos/modules/services/misc/subsonic.nix

@@ -1,8 +1,11 @@
-{ config, lib, pkgs, ... }:
+{ config, lib, options, pkgs, ... }:
 
 with lib;
 
-let cfg = config.services.subsonic; in {
+let
+  cfg = config.services.subsonic;
+  opt = options.services.subsonic;
+in {
   options = {
     services.subsonic = {
       enable = mkEnableOption "Subsonic daemon";
@@ -97,7 +100,7 @@ let cfg = config.services.subsonic; in {
         description = ''
           List of paths to transcoder executables that should be accessible
           from Subsonic. Symlinks will be created to each executable inside
-          ${cfg.home}/transcoders.
+          ''${config.${opt.home}}/transcoders.
         '';
       };
     };

nixos/modules/services/misc/zoneminder.nix

@@ -171,7 +171,7 @@ in {
         example = "/storage/tank";
         description = ''
           ZoneMinder can generate quite a lot of data, so in case you don't want
-          to use the default ${home}, you can override the path here.
+          to use the default ${defaultDir}, you can override the path here.
         '';
       };
 

nixos/modules/services/networking/ntopng.nix

@@ -1,10 +1,11 @@
-{ config, lib, pkgs, ... }:
+{ config, lib, options, pkgs, ... }:
 
 with lib;
 
 let
 
   cfg = config.services.ntopng;
+  opt = options.services.ntopng;
   redisCfg = config.services.redis;
 
   configFile = if cfg.configText != "" then
@@ -35,8 +36,8 @@ in
           collection tool.
 
           With the default configuration, ntopng monitors all network
-          interfaces and displays its findings at http://localhost:${toString
+          interfaces and displays its findings at http://localhost:''${toString
-          cfg.http-port}. Default username and password is admin/admin.
+          config.${opt.http-port}}. Default username and password is admin/admin.
 
           See the ntopng(8) manual page and http://www.ntop.org/products/ntop/
           for more info.

nixos/modules/services/web-apps/hedgedoc.nix

@@ -33,7 +33,7 @@ in
       type = types.listOf types.str;
       default = [];
       description = ''
-        Groups to which the user ${name} should be added.
+        Groups to which the service user should be added.
       '';
     };
 

nixos/modules/services/web-apps/matomo.nix

@@ -83,7 +83,7 @@ in {
         default = "${user}.${fqdn}";
         example = "matomo.yourdomain.org";
         description = ''
-          URL of the host, without https prefix. By default, this is ${user}.${fqdn}, but you may want to change it if you
+          URL of the host, without https prefix. You may want to change it if you
           run Matomo on a different URL than matomo.yourdomain.
         '';
       };