chunkiter: handle large reads more efficiently - for large reads, don't attempt to read more than necessary - if we've gathered the exact number of bytes needed, avoid a string copy

#!/bin/sh

hg
hg -q
hg help
hg -q help
hg add -h
hg add --skjdfks
hg help diff
hg help status
hg -q help status
hg help foo
hg skjdfks

exit 0