Merge branch 'jh/status-no-ahead-behind'

"git status" can spend a lot of cycles to compute the relation between the current branch and its upstream, which can now be disabled with "--no-ahead-behind" option. * jh/status-no-ahead-behind: status: support --no-ahead-behind in long format status: update short status to respect --no-ahead-behind status: add --[no-]ahead-behind to status and commit for V2 format. stat_tracking_info: return +1 when branches not equal