stablerange: directly use tuple to refer to a stable range Now that all advance logic lives in the unified class we no longer needs the individual class. Creating and operating on this cache introduce a significant overhead that we can not stop having. From now on, a range a is pair tuple '(headrev, index)'. Long live the tuple.

doc generated with sphinx. tutorial exported using sphinxedhg

http://hg.piranha.org.ua/sphinxedhg/