Merge branch 'js/safe-directory-plus' into maint

Platform-specific code that determines if a directory is OK to use
as a repository has been taught to report more details, especially
on Windows.
source: <redacted>

* js/safe-directory-plus:
  mingw: handle a file owned by the Administrators group correctly
  mingw: be more informative when ownership check fails on FAT32
  mingw: provide details about unsafe directories' ownership
  setup: prepare for more detailed "dubious ownership" messages
  setup: fix some formatting

diff --cc compat/mingw.c
Simple merge

diff --cc setup.c
Simple merge