modules/environment/session-init: add shellInit option to add custom shell code.

AUTHORS

@@ -3,3 +3,4 @@ Tobias Happ <tobias.happ@gmx.de>
 Bruno Bigras <bigras.bruno@gmail.com>
 Evgeny Kurnevsky <kurnevsky@gmail.com>
 Zhong Jianxin <azuwis@gmail.com>
+Shelvacu <nix-on-droid-is-cool@shelvacu.com>

modules/environment/session-init.nix

@@ -39,6 +39,8 @@ let
       ''}
 
       ${exportAll cfg.sessionVariables}
+
+      ${cfg.shellInit}
     '';
   };
 in
@@ -61,6 +63,16 @@ in
         '';
       };
 
+      shellInit = mkOption {
+        default = "";
+        type = types.lines;
+        description = ''
+          Shell script code called during shell initialization
+
+          This is useful to add custom aliases or functions, for example.
+        '';
+      };
+
       sessionVariables = mkOption {
         default = { };
         type = types.attrs;