too man macvim applet in docky while using gvimdiff as svn diff tool

i am using gvimdiff tool for svn diff:
svn_diff

#!/bin/bash

svn diff --diff-cmd diffwrap.sh "$@" 2>/dev/null

diffwrap.sh

#!/bin/bash

gvimdiff $6 $7

svn status:

M       trunk/main/main.cpp
M       trunk/principle/dllmain.cpp

while i type svn_diff in terminal, the terminal show:

Index: trunk/main/main.cpp
===================================================================
Index: trunk/principle/dllmain.cpp
===================================================================
2 files to edit
2 files to edit 

two diff files open(two macvim window show, and a new macvim applet shows in docky).
how to get one diff file and one macvim window per times ? that is, while i type svn_diff in terminal,
the terminal show:

Index: trunk/main/main.cpp
===================================================================

and i quit the macvim, next time, it show

Index: trunk/principle/dllmain.cpp
===================================================================

and one new macvim show simultaneously.
in the end, while finished svn_diff(:qa in gvim_diff per diff), two macvim applet in docky, on is default i put, another is a new one. every time i execute svn_diff, always a new macvim is stick to the docky if i do not quit it.

Reproduce the issue by running the mentioned svn_diff and diffwrap.sh scripts with multiple modified files, then inspect how gvimdiff launches MacVim windows and dock applets. Done means successive diffs use one MacVim window and do not leave an extra dock applet after the session ends.