'Diff paths against previous versions.'

def diff_predecessor(self):

    paths = self.selected_tracked_paths()
    args = ([u'--'] + paths)
    (revs, summaries) = gitcmds.log_helper(all=False, extra_args=args)
    commits = select_commits(N_(u'Select    Previous    Version'), revs, summaries, multiselect=False)
    if (not commits):
        return
    commit = commits[0]
    cmds.difftool_launch(left=commit, paths=paths)
