code: def do_diff(self, subcmd, opts, *args):
          
          print "'svn %s' opts: %s" % (subcmd, opts)
          print "'svn %s' args: %s" % (subcmd, args)
docs: Display the differences between two paths.
  
          usage:
              1. diff [-r N[:M]] [TARGET[@REV]...]
              2. diff [-r N[:M]] --old=OLD-TGT[@OLDREV] [--new=NEW-TGT[@NEWREV]] \
                      [PATH...]
              3. diff OLD-URL[@OLDREV] NEW-URL[@NEWREV]
          
          1. Display the changes made to TARGETs as they are seen in REV between
             two revisions.  TARGETs may be working copy paths or URLs.
          
             N defaults to BASE if any TARGET is a working copy path, otherwise it
             must be specified.  M defaults to the current working version if any
             TARGET is a working copy path, otherwise it defaults to HEAD.
          
          2. Display the differences between OLD-TGT as it was seen in OLDREV and
             NEW-TGT as it was seen in NEWREV.  PATHs, if given, are relative to
             OLD-TGT and NEW-TGT and restrict the output to differences for those
             paths.  OLD-TGT and NEW-TGT may be working copy paths or URL[@REV]. 
             NEW-TGT defaults to OLD-TGT if not specified.  -r N makes OLDREV default
             to N, -r N:M makes OLDREV default to N and NEWREV default to M.
          
          3. Shorthand for 'svn diff --old=OLD-URL[@OLDREV] --new=NEW-URL[@NEWREV]'
          
          Use just 'svn diff' to display local modifications in a working copy.
  
          ${cmd_option_list}