This catches up with changes in libgit2:
commit 9d7ac675d06dab2e000ad32f9248631af0191f85
Author: nulltoken <emeric.fermas@gmail.com>
Date: Tue Aug 21 11:45:16 2012 +0200
tree entry: rename git_tree_entry_attributes() into git_tree_entry_filemode()
If the user passes a tree, use it as the source for the
TreeBuilder. On the way, make sure we free the tree we looked up, and
fix a test to make sure the TreeBuilder starts empty.