Merge branch 'cc/lop-filter-auto' into seen

Merge branch 'cc/lop-filter-auto' into seen

"auto filter" logic for large-object promisor remote.

Comments?

* cc/lop-filter-auto:
  fetch-pack: wire up and enable auto filter logic
  promisor-remote: keep advertised filter in memory
  list-objects-filter-options: implement auto filter resolution
  list-objects-filter-options: support 'auto' mode for --filter
  doc: fetch: document `--filter=<filter-spec>` option
  fetch: make filter_options local to cmd_fetch()
  clone: make filter_options local to cmd_clone()
  promisor-remote: allow a client to store fields
  promisor-remote: refactor initialising field lists