I just now (re-)read the document "MSYS_VS_CYGWIN"
where it explains that the
observations I made below are by design, but it
doesn't explain why it was set up that way.
What's the advantage of setting things up that
$ mkdir usr
mkdir: cannot create directory 'usr': File
$ cd usr
$ ls usr (lists contents of "/"
$ cd /
$ mkdir tmp
$ cd tmp
$ ls tmp (lists contents of