environment.motd: add option

CHANGELOG.md

@@ -19,6 +19,8 @@
 * In an effort to reduce the number of arguments to `lib.nixOnDroidConfiguration`
   function in flake configurations, `system` is now inferred from `pkgs.system`
   and `config` and `extraModules` are now combined into `modules`
+* Add option `environment.motd` to edit the startup message that is printed in
+  every shell
 
 ## Release 22.05
 

modules/environment/login/login-inner.nix

@@ -13,10 +13,11 @@ writeText "login-inner" ''
 
   set -eo pipefail
 
+  ${lib.optionalString (config.environment.motd != null) ''
     if [ "$#" -eq 0 ]; then  # if script is called from within nix-on-droid app
-    echo "Welcome to Nix-on-Droid!"
-    echo "If nothing works, open an issue at https://github.com/t184256/nix-on-droid/issues or try the rescue shell."
+      echo "${lib.removeSuffix "\n" config.environment.motd}"
     fi
+  ''}
 
   ${lib.optionalString config.build.initialBuild ''
     if [ -e /etc/UNINTIALISED ]; then

modules/environment/session-init.nix

@@ -1,4 +1,4 @@
-# Copyright (c) 2019-2020, see AUTHORS. Licensed under MIT License, see LICENSE.
+# Copyright (c) 2019-2022, see AUTHORS. Licensed under MIT License, see LICENSE.
 
 { config, lib, pkgs, ... }:
 
@@ -49,7 +49,19 @@ in
 
   options = {
 
-    environment.sessionVariables = mkOption {
+    environment = {
+      motd = mkOption {
+        default = ''
+          Welcome to Nix-on-Droid!
+          If nothing works, open an issue at https://github.com/t184256/nix-on-droid/issues or try the rescue shell.
+        '';
+        type = types.nullOr types.lines;
+        description = ''
+          Text to show on every new shell created by nix-on-droid.
+        '';
+      };
+
+      sessionVariables = mkOption {
         default = { };
         type = types.attrs;
         example = { EDITOR = "emacs"; GS_OPTIONS = "-sPAPERSIZE=a4"; };
@@ -85,6 +97,7 @@ in
           </programlisting>
         '';
       };
+    };
 
   };