[PATCH 0/5] gc: minor code cleanup + contention fixes

[45]/5 fix a couple of issues I noted upthread. While I was at it I noticed a few things I could clean up in [123]/5 that I figured I'd send alongside this.

Ævar Arnfjörð Bjarmason (5):
  gc: remove redundant check for gc_auto_threshold
  gc: convert to using the_hash_algo
  gc: refactor a "call me once" pattern
  gc: don't run "reflog expire" when keeping reflogs
  reflog expire: don't assert the OID when locking refs

 builtin/gc.c         | 33 +++++++++++++++++++++++++--------
 refs/files-backend.c |  2 +-
 t/t6500-gc.sh        | 19 +++++++++++++++++++
 3 files changed, 45 insertions(+), 9 deletions(-)