Merge branch 'bp/refresh-index-using-preload'

The helper function to refresh the cached stat information in the
in-core index has learned to perform the lstat() part of the
operation in parallel on multi-core platforms.

* bp/refresh-index-using-preload:
  refresh_index: remove unnecessary calls to preload_index()
  speed up refresh_index() by utilizing preload_index()

diff --cc cache.h
Simple merge

diff --cc read-cache.c
Simple merge

diff --cc sequencer.c
Simple merge