cmdutil: make getgraphlogrevs return revs in descending order

branchmap: takes filtered revision in account for cache calculation Tracking tipnode and tiprev is not enough to ensure validaty of the cache as they do not help distinguish a cache that ignored various revisions below tiprev. To detect such difference, we build a hash of all ignored revisions. This hash is then used when checking the validity of a cache for a repo.

branchmap: improve computation of target tip With revision filtering the effective revision number of "tip" may be lower than: len(changelog) - 1 We now use a more correct version preventing useless writing on disk in some case.

branchmap: improve invalid cache message when reading This factors out the generation of the message. This helps future error reporting when reading cache for filtered repository.

histedit: allow operation from non-head if obsolete is enabled Obsolescence markers can represent this situation just fine. Rewritten revisions are marked as precursors of the ones creates by histedit. Unaffected descendants become "unstable". If obsolescence is not enabled we keep the current behavior of aborting. This new behavior only applies when obsolete is enabled and is subject to future discussion and changes.

rebase: allow non-head rebase-set when obsolete is enabled Obsolescence markers can represent this situation just fine. Rebased revisions are marked as precursors of the ones create by rebase. Unrebased descendants becomes "unstable". If obsolescence is not enabled we keep the current behavior of aborting. This new behavior only applies when obsolete is enabled and is subject to future discussion and changes.

amend: allow amend of non-head when obsolete is enabled Obsolescence marker can represent this situation just fine. The old version is marked as precursor of the new changeset. All its descendants become "unstable". If obsolescence is not enabled we keep the current behavior of aborting. This new behavior only applies when obsolete is enabled and is subject to future discussion and changes.

obsolete: factorise troubles detection during push The use of the two methods introduced earlier allows a factorisation of the push code preventing push of troubled changeset.

obsolete: introduce a troubles method on context A troubled changeset may be affected by multiple trouble at the same time. This new method returns a list of all troubles affecting a changes.

obsolete: introduce a troubled method on context Allows to quickly check if a changeset is affected by any troubles. (troubles are: unstable, bumped and divergent)