[Mingw-msys] passing "-" on command line in MSYS sh

Hi,

It seems that sh incorrectly translates "-" symbols on the command line. 
I've added code to dump the command line parameters:
when running the following command under sh
../bin/ch_wave - -obo MSB -otype nist -o tmp/ch_wave.nist
program output (note the addition of "F:/msys/1.0/bin/c" to the first "-" 
argument):
---------------------------------------------------- 
command line parameters:
../bin/ch_wave.exe
-F:/msys/1.0/bin/c
-obo
MSB
-otype
nist
-o
tmp/ch_wave.nist
----------------------------------------------------- 
running the same program with the same arguments under gdb:
---------------------------------------------------- 
command line parameters:
../bin/ch_wave.exe
-
-obo
MSB
-otype
nist
-o
tmp/ch_wave.nist
---------------------------------------------------- 

Is this a bug or feature? Is there some way to escape the "-" character to 
pass it correctly to the program?

Thanks,
Tomer