use batmenv3.1 release tag in nix file

default.nix

@@ -10,13 +10,13 @@ with kapack.pkgs;
 
 let self = rec {
   # For my scheduler and user simulator (batmen), pin a specific git commit:
-  batmen = kapack.batsched.overrideAttrs (attr: rec {
+  batmen-31 = kapack.batsched.overrideAttrs (attr: rec {
     name = "batmen";
-    version = "222d7cd741cbec9d79512ffe4bef4278d9deece8"; # commit "refac: renonce->renounce to correct orthograph, #24. 'dm_user_renonce' now depracated" Oct 30 2023
+    version = "refs/tags/v3.1";
     src = kapack.pkgs.fetchgit rec {
       url = "https://gitlab.irit.fr/sepia-pub/mael/batmen.git";
       rev = version;
-      sha256 = "sha256-ScxhAg7mr2FdMMdPDz39wqhc2cHi7rGpM8Y3cNtg3YE=";
+      sha256 = "sha256-9wX9gKl4ANt6fL6saZRRRajbY1E24soGlmIZNEWg7sU=";
     };
   });
 
@@ -24,7 +24,7 @@ let self = rec {
     name = "exp_env";
     buildInputs = [
       kapack.batsim-420   # data center simulator
-      batmen              # scheduler + user simulator
+      batmen-31           # scheduler + user simulator
       kapack.batexpe      # tool to execute batsim instances
       kapack.evalys       # for data visualization
       (python3.withPackages