log: fix crash on empty revision with --copies switch If a revset is empty, .max() raises ValueError. I don't see any reason to recompute the revs, so I made it reuse the one returned by logcmdutil.getrevs(). If no revs specified by command line, the endrev will be smartset.spanset(repo) + 1, which is basically the same as len(repo), the default of getrenamedfn(). If --follow specified, revs.max() points to the working parent, which seems more correct.