git_index_read_tree() was exposing a parameter to provide the user with
a progress indicator. Unfortunately, due to the recursive nature of the
tree walk, the maximum number of items to process was unknown. Thus,
the indicator was only counting processed entries, without providing
any information how the number of remaining items.

Clone

Replace with the contents of 
git_index_read_tree_with_stats() and improve
documentation comments.

New variant of git_index_read_tree that fills in
the 'total' field of a git_indexer_stats struct
as it's walking the tree.