[PATCH v1 0/1] pack-refs: pack expired loose refs to packed_refs

From: Sun Chao <sunchao9@huawei.com>

When a packed ref is deleted, the whole packed-refs file is rewrite and omit the ref that no longer exists. However if another gc command is running and call `pack-refs --all` simultaneously, there is a change that a ref just updated will lost the newly commits.

There are two valid methods to avoid losting commit of ref:
  - force `update-ref -d` to update the snapshot before
    rewrite packed-refs.
  - do not pack a recently updated ref, where *recently*
    could be set by *pack.looserefsexpire* option.

I prefer **do not pack a recently updated ref**, here is the reasons:

  1. It could avoid losting the newly commit of a ref which I
     described upon.

  2. Sometime, the git server will do `pack-refs --all` and
     `update-ref` the same time, and the two commands have
     chances to trying lock the same ref such as master, if
     this happends one command will fail with such error:

     **cannot lock ref 'refs/heads/master'**

     This could happen if a ref is updated frequently, and
     avoid pack the ref which is update recently could avoid
     this error most of the time.

Sun Chao (1):
  pack-refs: pack expired loose refs to packed_refs

 builtin/pack-refs.c       | 13 ++++++++++++-
 refs.c                    |  4 ++--
 refs.h                    |  2 +-
 refs/files-backend.c      | 18 +++++++++++++++++-
 refs/packed-backend.c     |  2 +-
 refs/refs-internal.h      |  2 +-
 t/helper/test-ref-store.c |  2 +-
 7 files changed, 35 insertions(+), 8 deletions(-)