different fish exec workaround

Signed-off-by: Harald Hoyer <harald@hoyer.xyz>

modules/nixos/user/default.nix

@@ -78,7 +78,9 @@ in
         if [[ $(${pkgs.procps}/bin/ps --no-header --pid=$PPID --format=comm) != "fish" && -z ''${BASH_EXECUTION_STRING} ]]
         then
           shopt -q login_shell && LOGIN_OPTION='--login' || LOGIN_OPTION=""
-          exec ${pkgs.fish}/bin/fish $LOGIN_OPTION
+          SHELL=/run/current-system/sw/bin/fish exec ${pkgs.fish}/bin/fish $LOGIN_OPTION
+        else
+          [[ $SHELL == *fish ]] && SHELL=/run/current-system/sw/bin/bash
         fi
       '';
     };