The state of the object store series

There is an ongoing effort to remove global state currently and switch over to pass around the relevant data structures; for most of it we end up passing around 'the_repository' as it contains everything there is.

Merged into master:

fcb6df32546 Merge branch 'sb/oid-object-info' a2cec42213c Merge branch 'sb/object-store-replace' 3a1ec60c43b Merge branch 'sb/packfiles-in-repository' cf0b1793ead Merge branch 'sb/object-store'

Currently cooking:

8c69a7d7e80 Merge branch 'sb/object-store-grafts' into pu 42d32d07298 Merge branch 'sb/object-store-alloc' into jch

(both marked for "will merge to next" in the cooking report)

Floating on the mailing list, not cooking yet:

"sb/object-store-lookup"
https://public-inbox.org/git/20180613230522.55335-1-sbeller@google.com/
  This clashes with other series in flight (Stolees get_tree series; see
  https://public-inbox.org/git/709bd61c-70fc-a925-efba-58ab9be265c9@gmail.com/
  I'll rebase this series on top of that series once the currently cooking
  series stabilize)

"nd/kill-the_index"
https://public-inbox.org/git/20180616054157.32433-1-pclouds@gmail.com/
  This converts the_index to pass around index pointers instead of
the_repository;
  it fits into the theme, but Duys end goal differs from mine; he is
less submodule focused.

Work that still needs to be done:

"xx/object-store-commit-graph"
  Convert the commit graph to have no global state, but be part of the
  repository struct. I think this can go in parallel to
"sb/object-store-lookup",
  so I'll tackle that next. Thanks Stolee for looking ahead: There is only the
  commit graph itself as well as whether it has been prepared as a global
  variable. So this series will consist of passing around a repository struct
  for all those higher level functions that do not pass around the commit graph
  or parts of it.

"xx/finish-object-stores"
  This requires "xx/object-store-commit-graph" as well as
"sb/object-store-lookup";
  it will convert parse_commit[_gently] to take a repository argument and will
  finish the actual object store part. This might be optional for the goal of
  converting submodules, that I have in mind, but it sure is a nice finishing
  touch.

"xx/convert-revision-walking"
  This series aims to convert get_merge_bases(), in_merge_bases() and all its
  revision walking code to take a repository argument.

"xx/submodule-dont-use-alternates"
  Once "xx/convert-revision-walking" is in, convert the local
find_first_merges(),
  and convert all functions to drop function add_submodule_odb() and instead
  operate on the submodule repository instead of the_repository with the
  submodule objects added as an alternate.

Thanks, Stefan