Make changes -r+ as fast as prs -r+ by not walking the weave unless we are going to use weave data, and cutting syscalls flushing small buffers.
Make changes -r+ as fast as prs -r+ by not walking
the weave unless we are going to use weave data,
and cutting syscalls flushing small buffers.

bk: 4dd411291siRSPpucCRTt5jz-UzNbg
bitkeeper-scm/bitkeeper,bitkeeper-scm/bitkeeper,bitkeeper-scm/bitkeeper,bitkeeper-scm/bitkeeper,bitkeeper-scm/bitkeeper,bitkeeper-scm/bitkeeper,bitkeeper-scm/bitkeeper,bitkeeper-scm/bitkeeper,bitkeeper-scm/bitkeeper,bitkeeper-scm/bitkeeper,bitkeeper-scm/bitkeeper,bitkeeper-scm/bitkeeper