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.
running: init test1
result: None
running: add foo
result: 0
running: commit -m commit1 -d 2000-01-01 foo
result: None
running: commit -m commit2 -d 2000-01-02 foo
result: None
running: log -r 0
changeset: 0:0e4634943879
user: test
date: Sat Jan 01 00:00:00 2000 +0000
summary: commit1
result: None
running: log -r tip
changeset: 1:45589e459b2e
tag: tip
user: test
date: Sun Jan 02 00:00:00 2000 +0000
summary: commit2
result: None