Merge branch 'kb/name-hash'

The code to keep track of what directory names are known to Git on
platforms with case insensitive filesystems can get confused upon
a hash collision between these pathnames and looped forever.

* kb/name-hash:
  name-hash.c: fix endless loop with core.ignorecase=true

diff --cc cache.h
Simple merge

diff --cc name-hash.c
Simple merge

diff --cc read-cache.c
Simple merge