revset: raise ValueError when calling min or max on empty smartset
min([]) raise a ValueError, we do the same thing in smartset.min() and
smartset.max() for the sake of consistency.
The min/amax test are greatly improved in the process to prevent this familly
of regression
all()
draft()
::tip
draft() and ::tip
0::tip
roots(0::tip)
author(lmoscovicz)
author(mpm)
author(lmoscovicz) or author(mpm)
tip:0
max(tip:0)
min(0:tip)
0::
min(0::)
::p1(p1(tip))::