add worktree ease for local dev of my modules system

flake.nix

@@ -63,6 +63,7 @@
     {
       self,
       nypkgs,
+      nixpkgs_stable,
       cosmic,
       lio_nixpkgs,
       lio_home-manager,
@@ -147,6 +148,15 @@
         hostsDir = ./hosts_old;
         usersDir = ./users;
       };
+
+      # Utilities
+      inherit (nixpkgs_stable) lib;
+      # Define the systems to support (all Linux systems exposed by nixpkgs)
+      systems = lib.intersectLists lib.systems.flakeExposed lib.platforms.linux;
+      forAllSystems = lib.genAttrs systems;
+      # Create a mapping from system to corresponding nixpkgs : https://nixos.wiki/wiki/Overlays#In_a_Nix_flake
+      nixpkgsFor = forAllSystems (system: nixpkgs_stable.legacyPackages.${system});
+
     in
     {
       # foldl' is "reduce" where { } is the accumulator and myHosts is the array to reduce on.
@@ -186,5 +196,51 @@
             // nixConfig.opts;
         }
       ) { } myHosts;
+
+      devShells = forAllSystems (
+        system:
+        let
+          pkgs = nixpkgsFor.${system};
+
+          mod_worktrees = pkgs.writeShellScriptBin "mod_worktrees" ''
+            # Get all local and remote mod_* branches, removing lines with '+'
+            branches=$(git branch -a | grep -E 'mod_' | grep -v '^\s*+' | sed 's/^[* ]*//; s/^remotes\/origin\///')
+
+            # Remove duplicates and sort
+            branches=$(echo "$branches" | sort -u)
+
+            for branch in $branches; do
+                # Skip master or other non-mod branches
+                if [[ ! "$branch" =~ ^mod_ ]]; then
+                    continue
+                fi
+
+                # Derive module name (remove mod_ prefix)
+                module_name="''${branch#mod_}"
+                module_path="modules/$module_name"
+
+                # Check if worktree already exists
+                if [ ! -d "$module_path" ]; then
+                    echo "Adding worktree for $branch in $module_path"
+                    git worktree add "$module_path" "$branch" 2>/dev/null
+                # else
+                #     echo "Worktree for $branch already exists"
+                fi
+            done
+          '';
+        in
+        {
+          default = pkgs.mkShell {
+            nativeBuildInputs = [
+              mod_worktrees
+            ];
+
+            shellHook = ''
+              mod_worktrees
+            '';
+          };
+        }
+      );
+
     };
 }