git-gui: Display the directory basename in the title

By showing the basename of the directory very early in the
title bar I can more easily locate a particular git-gui
session when I have 8 open at once and my  Windows taskbar
is overflowing with items.
Signed-off-by: NShawn O. Pearce <spearce@spearce.org>

git-gui.sh

@@ -5968,7 +5968,7 @@ unset i
 set file_lists($ui_index) [list]
 set file_lists($ui_workdir) [list]
 
-wm title . "[appname] ([file normalize [file dirname [gitdir]]])"
+wm title . "[appname] ([reponame]) [file normalize [file dirname [gitdir]]]"
 focus -force $ui_comm
 
 # -- Warn the user about environmental problems.  Cygwin's Tcl