[PATCH/RFC 00/15] Fix git-gc losing objects in multi worktree

["Nguyễn Thái Ngọc Duy" <pclouds@gmail.com>]

So here is my latest attempt on fixing this issue. For people who are
not aware of it, git-gc does not take per-worktree refs, reflogs and
indexes into account. An odb prune may leave HEAD and references in other
worktrees pointing to nowhere.

This series is based on my "kill parse_ref()" series [1], which is
based on yet another one, which is on top of mh/submodule-hash. But
you can get everything from my github [2].

The series introduces a new set of refs_* API and replaces the old
*_submodule() one, opening up the opportunity to access refs from
another worktree. rev-list learns a new option, --single-worktree, to
control the new behavior.

reflog iterator from files-backend.c does not support per-worktree
items, so it's updated here to do that. It still looks ugly, but I
think this is a good "middle ground" until compound ref store comes.
At that point we can separate "single worktree" ref store vs "linked
worktree" one.

I'm adding Stefan here as well since I added a new FIXME in
submodule.c in 11/15. I think it's ok (again, for now). But another
look from submodule people would be much better.

[1] http://public-inbox.org/git/%3C20170216120302.5302-1-pclouds@gmail.com%3E/
[2] https://github.com/pclouds/git/commits/prune-in-worktrees-2

Nguyễn Thái Ngọc Duy (15):
  revision.h: new flag in struct rev_info wrt. worktree-related refs
  revision.c: refactor add_index_objects_to_pending()
  revision.c: --indexed-objects add objects from all worktrees
  refs: move submodule slash stripping code to get_submodule_ref_store
  refs: add refs_read_ref[_full]()
  refs: add refs_head_ref()
  refs: add refs_for_each_ref()
  refs: add a refs_for_each_in() and friends
  revision.c: use refs_for_each*() instead of for_each_*_submodule()
  refs: remove dead for_each_*_submodule()
  revision.c: --all adds HEAD from all worktrees
  refs: add refs_for_each_reflog[_ent]()
  files-backend: make reflog iterator go through per-worktree reflog
  revision.c: --reflog add HEAD reflog from all worktrees
  rev-list: expose and document --single-worktree

 Documentation/rev-list-options.txt |   8 ++
 reachable.c                        |   1 +
 refs.c                             | 171 ++++++++++++++++++++++++-------------
 refs.h                             |  25 ++++--
 refs/files-backend.c               |  24 +++++-
 revision.c                         | 130 +++++++++++++++++++++++-----
 revision.h                         |   1 +
 submodule.c                        |   2 +
 t/t5304-prune.sh                   |  37 ++++++++
 9 files changed, 305 insertions(+), 94 deletions(-)

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2.11.0.157.gd943d85