260 

   261 @registerformatvariant

   262 class sparserevlog(requirementformatvariant):

   263     name = 'sparserevlog'

   264 

   265     _requirement = localrepo.SPARSEREVLOG_REQUIREMENT

   266 

   267     default = False

   268 

   269     description = _('in order to limit disk reading and memory usage on older '

   270                     'version, the span of a delta chain from its root to its '

   271                     'end is limited, whatever the relevant data in this span. '

   272                     'This can severly limit Mercurial ability to build good '

   273                     'chain of delta resulting is much more storage space being '

   274                     'taken and limit reusability of on disk delta during '

   275                     'exchange.'

   276                    )

   277 

   278     upgrademessage = _('Revlog supports delta chain with more unused data '

   279                        'between payload. These gaps will be skipped at read '

   280                        'time. This allows for better delta chains, making a '

   281                        'better compression and faster exchange with server.')