test: adapt to 3.6 help changes

evolve: make split respect rev args passed without --rev or -r Currently, if one runs `hg split .` or `hg split`, it will fail with an exception. This happens becuase we only expect revision args to be passed as --rev/-r ones and don't treat unnamed args properly or add default values if no args are provided.

evolve: write our own custom evolvestate file Since for ever, we were using 'graftstate' to record the node currently being evolve and allow 'hg evolve --continue' we now move to our on 'evolvestate' file. This remove and issue with 'hg summary' listing interrupted evolve as graft. This also open the way for storing more data into that file and allow proper --abort and --continue of the whole evolve operation (and not just the last one). The whole thing is very hacky but at least there is some progress. Thanks goes to Shusen Liu for initiating this work.