[PATCH 0/2] prevent `repack` to unpack and delete promisor objects

This series is built on top of jk/promisor-optim. It conflicts with changes on p5600 otherwise.

The following patches fixes the issue where we unnecessarily turn loose all the promisor objects and deletes them right after when running `repack -A -d ..` (via `git gc) for a partial repository.

Special thanks to Peff, for proposing a better approach for managing the situation and for Jonathan Tan for earlier interaction on the solution. Previously, I thought we should skip the promisor objects by just adding a check in loosened_object_can_be_discarded(). However, Peff pointed out that we can do better by realizing much sooner that we should not even consider loosening the objects for the _old_ promisor packs.

It took me a bit to come up with the test because it seems `repack` doesn't offer an option to skip the "deletion of unpacked objects", so this series adds a new option to `repack` for skip the `git prune-packed` execution thus allowing us to easily inspect the unpacked objects before they are removed and simplification of our test suite. Furthermore, The test will now test the `repack` code path instead of performing the operations by calling `pack-objects`.

Rafael Silva (2):
  repack: teach --no-prune-packed to skip `git prune-packed`
  repack: avoid loosening promisor pack objects in partial clones

 Documentation/git-repack.txt  |  5 +++++
 builtin/repack.c              | 15 ++++++++++++---
 t/perf/p5600-partial-clone.sh |  4 ++++
 t/t5616-partial-clone.sh      |  9 +++++++++
 t/t7700-repack.sh             | 23 +++++++++++------------
 5 files changed, 41 insertions(+), 15 deletions(-)