Clarify uses of xml.dom.
Clarify uses of xml.dom.

* contrib/client-side/svnmerge/svnmerge.py
  (getAttributeOrNone): New function.
  (SvnLogParser): provide more informative error message if expected name is
    not found.
  (SvnLogRevision): call getAttributeOrNone instead of
    xml.dom.Element.getAttribute directly, to integrate more cleanly with
    get_copyfrom() by returning None instead of an empty string.

Patch by: Luke Call <lacall186@onemodel.org>
Review by: Giovanni Bajo <rasky@develer.com>


git-svn-id: f8a4e5e023278da1e04e203c7fe051e3c4285d88@865945 13f79535-47bb-0310-9956-ffa450edef68

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