obsdiscovery: extract push-obshashrange discovery in a function This will help us to simplify the code. The code is updated to directly use 'outgoing' missing so that is no longer needs to access 'futureheads'.

obsdiscovery: merge two distinct if statement It did not made any sense for them to be split.

obsdiscovery: extract '_canobshashtree' having this as a simple function will help use to generalise the obsdiscovery algorithm we use.

obsdiscovery: move code inserting discovery at the end of the file This makes it easier to reuser function defined earlier in the file.

obsdiscovery: trust core to do the right thing if no discovery is available This is fixed for a long time now.

obsdiscovery: factor the "do we push markers" check out This clarify the code a bit.

stablerange: also respect the 'warm-cache' config This will help large install to enable obshashrange as "opt-in" without impacting other repositories.

debugstablerange: cleanly "Abort" when no revision are specified Previously we had a traceback from a max on an empty sequence.

stablerange: use last recently used caching for revisions associated to ranges This does not make things faster but at least it make them able to finish on large repositories.

stablerange: report progress more often in slow case For small repositories the time spent in progress was problematic. However on large repository it quickly becomes negligible, so we add a way to detect this case and report more often in this case.