Index: /trunk/Mars/hawc/mcmerpp.C
===================================================================
--- /trunk/Mars/hawc/mcmerpp.C	(revision 19701)
+++ /trunk/Mars/hawc/mcmerpp.C	(revision 19701)
@@ -0,0 +1,39 @@
+int mcmerpp(const char *fin="ceres.root", const char *fout="star.root")
+{
+    TFile filein (fin,  "READ");
+    if (!filein)
+    {
+        cerr << "Failed to open '" << fin << "'" << endl;
+        return -1;
+    }
+
+    TFile fileout(fout, "UPDATE");
+    if (!fileout)
+    {
+        cerr << "Failed to open '" << fout << "'" << endl;
+        return -1;
+    }
+
+
+    TTree *tree = dynamic_cast<TTree*>(filein.Get("OriginalMC"));
+    if (!tree)
+    {
+        cerr << "Tree 'OriginalMC' not found in '" << fin << "'" << endl;
+        return -1;
+    }
+
+    //tree->SetBranchStatus("*", 1);
+
+    // Now we clone the tree without unpacking and repacking.
+    // When it has not been moved it will be deleted in the TFile destructor
+
+    TTree *newtree = tree->CloneTree(-1, "fast SortBasketsByEntry");
+    if (!newtree)
+        return -1;
+    newtree->Write();
+    delete newtree;
+
+    cerr << "OriginalMC copied from '" << fin << "' to '" << fout << "'" << endl;
+
+    return 0;
+}