"hg mv" cannot change case on windows, and "hg status" does not notice it either

[rupert.thurner]

while the operating system can change the case of a file, mercurial
cannot on windows:

$ echo bla > ts
$ hg init
$ hg st
$ hg add ts
$ hg commit -m "as "
$ hg mv ts Ts
Ts: not overwriting - file exists
$ mv ts Ts
$ ls -l
total 1
-rw-r--r--    1 me Administ        4 Jun  5 19:29 Ts

this test was done with msys, but the same is true for cmd, etc. is
this a mercurial bug, or a python thing?