setdiscovery: drop unused 'initial' argument for '_takequicksample' There is a single call site, and it is always using 'initial=True'. So we just drop the argument and the associated condition.

readmarkers: add a SHA256 fixme note

readmarkers: fast-path single successors and parents This gives about a 5% performance bump.

readmarkers: promote global constants to locals for performance

readmarkers: drop a temporary

readmarkers: read node reading into node length conditional This removes some conditional assignments

readmarkers: drop a temporary Two other temporaries are renamed to fit line-length.

readmarkers: hoist subtraction out of loop comparison

readmarkers: streamline offset tracking This minimizes the number of assignments and operations needed to use offsets.

readmarkers: use unpacker for fixed header

readmarkers: drop metadata temporary

readmarkers: drop date temporary

readmarkers: drop another conditional

readmarkers: drop a conditional

readmarkers: add some whitespace

readmarkers: combine parent conditionals