def SetVersionNumber(RevString):
    """Set the subversion version number

    :param str RevString: something like "$Revision: 4155 $"
      that is set by subversion when the file is retrieved from subversion.

    Place ``GSASIIpath.SetVersionNumber("$Revision: 4155 $")`` in every python
    file.
    """
    try:
        RevVersion = int(RevString.split(':')[1].split()[0])
        global version
        version = max(version, RevVersion)
    except:
        pass
