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.