Merge branch 'js/icase-wt-detection'

On a case insensitive filesystems, setting GIT_WORK_TREE variable
using a random cases that does not agree with what the filesystem
thinks confused Git that it wasn't inside the working tree.

* js/icase-wt-detection:
  setup: fix "inside work tree" detection on case-insensitive filesystems

diff --cc dir.c
Simple merge