[PATCH 0 of 2] bisect: add new revset ranges and cleanup code, v2

[Yann E. MORIN]

Hello All!

This patchset drastically cleans up the code to compute bisect revsets.
It uses repo.set() wherever possible, instead of manually computing
complex ranges.

Also, the meaning of the 'pruned' keyword has been revised to mean 'every
csets whose fate is already known', and that can't take part to the
bisection anymore.

Finally, a new set keyword has been added to list all csets that are
ignored by the bisection. See comments in corresponding patch.

Changes since v1:
 - use a single revset query instead of multiple ones (Matt)
 - drop the 'remaining' keyword, covered by 'untested' (Matt)
 
Regards,
Yann E. MORIN.