git-gui: open console when using --trace on windows

When starting a gui program on windows stdout, stderr and stdin are not
connected to the cmd console. As a workaround tk has a console window.
Lets open this when the --trace commandline option has been given.
This is helpful for debugging.

Signed-off-by: Heiko Voigt <hvoigt@hvoigt.net>
Signed-off-by: Pat Thoyts <patthoyts@users.sourceforge.net>

git-gui.sh

@@ -154,6 +154,7 @@ set _trace [lsearch -exact $argv --trace]
 if {$_trace >= 0} {
 	set argv [lreplace $argv $_trace $_trace]
 	set _trace 1
+	if {[tk windowingsystem] eq "win32"} { console show }
 } else {
 	set _trace 0
 }