where read_from_tree() internally also calls
update_index_refresh(). Move the call to update_index_refresh() out of
read_from_tree for symmetry with the 'else' block, making
read_from_tree() and reset_index() closer in functionality.
Signed-off-by: Martin von Zweigbergk <martinvonz@gmail.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>