Merge branch 'ps/avoid-unnecessary-hook-invocation-with-packed-refs'

Because a deletion of ref would need to remove it from both the
loose ref store and the packed ref store, a delete-ref operation
that logically removes one ref may end up invoking ref-transaction
hook twice, which has been corrected.

* ps/avoid-unnecessary-hook-invocation-with-packed-refs:
  refs: skip hooks when deleting uncovered packed refs
  refs: do not execute reference-transaction hook on packing refs
  refs: demonstrate excessive execution of the reference-transaction hook
  refs: allow skipping the reference-transaction hook
  refs: allow passing flags when beginning transactions
  refs: extract packed_refs_delete_refs() to allow control of transaction

diff --cc refs.c
Simple merge

diff --cc refs.h
Simple merge

diff --cc refs/files-backend.c
Simple merge

diff --cc refs/packed-backend.c
Simple merge

diff --cc refs/packed-backend.h
Simple merge

diff --cc refs/refs-internal.h
Simple merge

diff --cc sequencer.c
Simple merge