From Philippe;

This patch adds support in the new tree cloning scheme for
        TTree *clone = chain->GetTree()->CloneTree(0);
If chain is really a TChain, need to make sure that it keeps track of the clones even when the tree that was
actually cloned is deleted by LoadTree.


git-svn-id: http://root.cern.ch/svn/root/trunk@6848 27541ba8-7e3a-0410-8455-c3a389f83636

tree/inc/TTree.h

-// @(#)root/tree:$Name:  $:$Id: TTree.h,v 1.47 2003/06/30 15:45:52 brun Exp $
+// @(#)root/tree:$Name:  $:$Id: TTree.h,v 1.48 2003/07/04 13:27:35 brun Exp $
 // Author: Rene Brun   12/01/96
 
 /*************************************************************************
@@ -201,6 +201,7 @@ public:
     virtual Double_t *GetIndexValues() {return &fIndexValues.fArray[0];}
     virtual TIterator*GetIteratorOnAllLeaves(Bool_t dir = kIterForward);
     virtual TLeaf    *GetLeaf(const char *name);
+    virtual TList    *GetListOfClones() { return fClones; }
     virtual TObjArray       *GetListOfBranches() {return &fBranches;}
     virtual TObjArray       *GetListOfLeaves()   {return &fLeaves;}
     virtual TList    *GetListOfFriends() const  {return fFriends;}

tree/src/TChain.cxx

-// @(#)root/tree:$Name:  $:$Id: TChain.cxx,v 1.71 2003/07/06 19:41:49 brun Exp $
+// @(#)root/tree:$Name:  $:$Id: TChain.cxx,v 1.72 2003/07/06 19:44:31 brun Exp $
 // Author: Rene Brun   03/02/97
 
 /*************************************************************************
@@ -750,6 +750,19 @@ Int_t TChain::LoadTree(Int_t entry)
       return fReadEntry;
    }
 
+   // If the tree has some clone, let migrate them into the chain so we can
+   // continue to keep track of it.  This is to support the syntax: 
+   //    clone = (TTree*)chain->GetTree()->CloneTree(0)
+   if (fTree && fTree->GetListOfClones()) {
+      TObjLink *lnk = fTree->GetListOfClones()->FirstLink();
+      while (lnk) {
+         TTree *clone = (TTree*)lnk->GetObject();
+         AddClone(clone);
+         lnk = lnk->Next();
+      }
+      fTree->GetListOfClones()->Clear(); 
+   }
+
    //Delete current tree and connect new tree
    TDirectory *cursav = gDirectory;
    //delete file unless the file owns this chain !!