Merge branch 'kb/lstat-cache'

* kb/lstat-cache:
lstat_cache(): introduce clear_lstat_cache() function
lstat_cache(): introduce invalidate_lstat_cache() function
lstat_cache(): introduce has_dirs_only_path() function
lstat_cache(): introduce has_symlink_or_noent_leading_path() function
lstat_cache(): more cache effective symlink/directory detection

diff --cc cache.h
Simple merge

diff --cc entry.c
Simple merge

diff --cc unpack-trees.c
Simple merge