use latest version of batmen (with corrected easy_bf_fast)

default.nix

@@ -25,9 +25,10 @@ let self = rec {
   batmen = kapack.batsched.overrideAttrs (attr: rec {
     name = "batmen";
     version = "refs/tags/replay_feedback2023";
-    src = fetchGit rec {
+    src = fetchgit rec {
       url = "https://gitlab.irit.fr/sepia-pub/mael/batmen.git";
-      ref = version;
+      rev = version;
+      sha256 = "sha256-YRL+cehPDZP5zqZEhFIuf5DpF8rG5UhLs1oDnuM5U5Q=";
     };
   });