Re: [ot][spam][crazy] crazylog: append-only random-access data

so a write has two ends, a start and an end, and each one can either be within an old write, within an old flush, or in a new area. then similarly, they can span all or parts of writes and flushes, as well. the old code uses start_idx and end_idx and then excises that range. the ends are treated specially. the most important part seems to be adjusting their bounds. if a write or a flush is partially cut, its bounds can be adjusted, and if it is a flush then it can be further optimised as it will have lost leaves.