Modularize some sets of repeated operations in svn2rss.py.
Modularize some sets of repeated operations in svn2rss.py.

* contrib/hook-scripts/svn2rss.py
  (usage): Remove.
  (usage_and_exit): New.
  (__main__): Use usage_and_exit() instead of usage().
  


git-svn-id: f8a4e5e023278da1e04e203c7fe051e3c4285d88@860217 13f79535-47bb-0310-9956-ffa450edef68

YueLinHo/Subversion,wbond/subversion,YueLinHo/Subversion,YueLinHo/Subversion,YueLinHo/Subversion,wbond/subversion,wbond/subversion,wbond/subversion,wbond/subversion,YueLinHo/Subversion,YueLinHo/Subversion,YueLinHo/Subversion,wbond/subversion,YueLinHo/Subversion,wbond/subversion