gitview: pass the missing argument _show_clicked_cb.

In our last update to use the encoding while showing the commit
diff we added a new argument to this function. But we missed
updating all the callers.

Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@gmail.com>
Signed-off-by: Junio C Hamano <junkio@cox.net>

contrib/gitview/gitview

@@ -798,7 +798,7 @@ class GitView:
 			button.set_relief(gtk.RELIEF_NONE)
 			button.set_sensitive(True)
 			button.connect("clicked", self._show_clicked_cb,
-					child_id, commit.commit_sha1)
+					child_id, commit.commit_sha1, self.encoding)
 			hbox.pack_start(button, expand=False, fill=True)
 			button.show()