obshashrange: always save stable range cache alongside the obshashrange one If the on disk date cover different area, the invalidation of affected range will misbehave.

obshashrange: clear in-memory cache alongside the sqlite one Clearing on disk data in nice, but we also need to remove in memory one or we'll get incorrect results.

branching: merge with fixes on stable

changelog: summarize the recent improvement

obshashrange: re-enabled more selective pruning of affected range

obshashrange: fix computation of affected ranges The computation of impacted nodes and associated revs is fully reworked. In addition,we introduce multiple new tests covering cases that were previous wrongly handled.