Merge branch 'cc/repack-sift-filtered-objects-to-separate-pack'

"git repack" machinery learns to pay attention to the "--filter="
option.

* cc/repack-sift-filtered-objects-to-separate-pack:
  gc: add `gc.repackFilterTo` config option
  repack: implement `--filter-to` for storing filtered out objects
  gc: add `gc.repackFilter` config option
  repack: add `--filter=<filter-spec>` option
  pack-bitmap-write: rebuild using new bitmap when remapping
  repack: refactor finding pack prefix
  repack: refactor finishing pack-objects command
  t/helper: add 'find-pack' test-tool
  pack-objects: allow `--filter` without `--stdout`

diff --cc Makefile
Simple merge