different fish exec workaround

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

flake.lock

@@ -2507,11 +2507,11 @@
     },
     "unstable": {
       "locked": {
-        "lastModified": 1710806803,
-        "narHash": "sha256-qrxvLS888pNJFwJdK+hf1wpRCSQcqA6W5+Ox202NDa0=",
+        "lastModified": 1711163522,
+        "narHash": "sha256-YN/Ciidm+A0fmJPWlHBGvVkcarYWSC+s3NTPk/P+q3c=",
         "owner": "nixos",
         "repo": "nixpkgs",
-        "rev": "b06025f1533a1e07b6db3e75151caa155d1c7eb3",
+        "rev": "44d0940ea560dee511026a53f0e2e2cde489b4d4",
         "type": "github"
       },
       "original": {

modules/nixos/user/default.nix

@@ -73,8 +73,15 @@ in
         }".source =
           cfg.icon;
       };
+
       extraOptions.programs.bash.initExtra = ''
-        [[ $WANT_BASH ]] || exec ${pkgs.fish}/bin/fish -l
+        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=""
+          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
       '';
     };