git-gui: Paper bag fix the global config parsing

git-config won't honor any options after --list.  We must supply
the --global option in front of --list if we really want to load
the global configuration options.
Signed-off-by: NShawn O. Pearce <spearce@spearce.org>

git-gui.sh

@@ -755,7 +755,10 @@ git-version proc _parse_config {arr_name args} {
 		array unset arr
 		set buf {}
 		catch {
-			set fd_rc [eval [list git_read config --null --list] $args]
+			set fd_rc [eval \
+				[list git_read config] \
+				$args \
+				[list --null --list]]
 			fconfigure $fd_rc -translation binary
 			set buf [read $fd_rc]
 			close $fd_rc