[Rivet] Branched release-2-0

[David Grellscheid]

> What's the difference between
> 
> hg clone -r release-2-0 http://rivet.hepforge.org/hg/rivet
> hg clone -b release-2-0 http://rivet.hepforge.org/hg/rivet

In this case, none. The options are both there for symmetry with other
commands, and have slightly different semantics. "-r" takes revision
labels, "-b" takes branch labels.

But a branch label can be used as a revision label: it is a synonym for
the head revision in a branch.

See you,

  David