Merge branch 'jl/pack-transfer-avoid-double-close'

The codepath that send_pack() calls pack_objects() mistakenly
closed the same file descriptor twice, leading to potentially
closing a wrong file descriptor that was opened in the meantime.

* jl/pack-transfer-avoid-double-close:
  Clear fd after closing to avoid double-close error

diff --cc fetch-pack.c
Simple merge

diff --cc send-pack.c
Simple merge