TTree::MergeTrees pass options to first Cloning.
TTree::MergeTrees pass options to first Cloning.

This allow the fast cloning of the first tree in the list when using TTree::MergeTrees (rare)

olifre/root,olifre/root,root-mirror/root,olifre/root,root-mirror/root,root-mirror/root,olifre/root,root-mirror/root,olifre/root,root-mirror/root,olifre/root,olifre/root,root-mirror/root,root-mirror/root,root-mirror/root,root-mirror/root,olifre/root,olifre/root,root-mirror/root,root-mirror/root,olifre/root,olifre/root