[PATCH v4 0/7] No more adding submodule ODB as alternate

Thanks everyone for your reviews. Here's an updated patch set, including Carlo's fixup squashed.

Jonathan Tan (7):
  refs: plumb repo into ref stores
  refs: teach arbitrary repo support to iterators
  refs: peeling non-the_repository iterators is BUG
  merge-{ort,recursive}: remove add_submodule_odb()
  object-file: only register submodule ODB if needed
  submodule: pass repo to check_has_commit()
  submodule: trace adding submodule ODB as alternate

 merge-ort.c                            | 18 +++--------
 merge-recursive.c                      | 41 +++++++++++++-------------
 object-file.c                          |  9 +++++-
 refs.c                                 | 32 +++++++++++++++-----
 refs/files-backend.c                   | 16 ++++++----
 refs/packed-backend.c                  | 13 ++++++--
 refs/packed-backend.h                  |  4 ++-
 refs/ref-cache.c                       | 10 +++++++
 refs/ref-cache.h                       |  1 +
 refs/refs-internal.h                   | 11 +++++--
 strbuf.c                               | 12 ++++++--
 strbuf.h                               |  6 ++--
 submodule.c                            | 18 +++++++++--
 t/README                               |  7 ++---
 t/t5526-fetch-submodules.sh            |  3 ++
 t/t5531-deep-submodule-push.sh         |  3 ++
 t/t5545-push-options.sh                |  3 ++
 t/t5572-pull-submodule.sh              |  3 ++
 t/t6437-submodule-merge.sh             |  3 ++
 t/t7418-submodule-sparse-gitmodules.sh |  3 ++
 20 files changed, 148 insertions(+), 68 deletions(-)

Range-diff against v3:
1:  878c4dd288 ! 1:  f050191d4c refs: plumb repo into ref stores
    @@ Commit message
         arbitrary repositories to ref iterators, plumb a repository into all ref
         stores. There are no changes to program logic.
     
    -    (The repository is plumbed into the ref stores instead of directly into
    -    the ref iterators themselves, so that existing code that operates on ref
    -    stores do not need to be modified to also handle repositories.)
    -
         Signed-off-by: Jonathan Tan <jonathantanmy@google.com>
         Signed-off-by: Junio C Hamano <gitster@pobox.com>
     
    @@ refs/packed-backend.c: static int release_snapshot(struct snapshot *snapshot)
      
     
      ## refs/packed-backend.h ##
    +@@
    + #ifndef REFS_PACKED_BACKEND_H
    + #define REFS_PACKED_BACKEND_H
    + 
    ++struct repository;
    + struct ref_transaction;
    + 
    + /*
     @@ refs/packed-backend.h: struct ref_transaction;
       * even among packed refs.
       */
2:  7180f622b1 = 2:  6418256919 refs: teach arbitrary repo support to iterators
3:  1a2e2e3e08 = 3:  d624c198d6 refs: peeling non-the_repository iterators is BUG
4:  89347503af = 4:  f3df7a31cb merge-{ort,recursive}: remove add_submodule_odb()
5:  17d6c0a793 ! 5:  78473b0f89 object-file: only register submodule ODB if needed
    @@ object-file.c: static int do_oid_object_info_extended(struct repository *r,
      		}
      
     -		if (register_all_submodule_odb_as_alternates())
    ++		/*
    ++		 * If r is the_repository, this might be an attempt at
    ++		 * accessing a submodule object as if it were in the_repository
    ++		 * (having called add_submodule_odb() on that submodule's ODB).
    ++		 * If any such ODBs exist, register them and try again.
    ++		 */
     +		if (r == the_repository &&
     +		    register_all_submodule_odb_as_alternates())
      			/* We added some alternates; retry */
6:  1eb2dda2dc = 6:  f4241ea2e7 submodule: pass repo to check_has_commit()
7:  36e741dda8 ! 7:  8922bf48a2 submodule: trace adding submodule ODB as alternate
    @@ submodule.c: int register_all_submodule_odb_as_alternates(void)
      		if (git_env_bool("GIT_TEST_FATAL_REGISTER_SUBMODULE_ODB", 0))
      			BUG("register_all_submodule_odb_as_alternates() called");
      	}
    +
    + ## t/README ##
    +@@ t/README: GIT_TEST_FATAL_REGISTER_SUBMODULE_ODB=<boolean>, when true, makes
    + registering submodule ODBs as alternates a fatal action. Support for
    + this environment variable can be removed once the migration to
    + explicitly providing repositories when accessing submodule objects is
    +-complete (in which case we might want to replace this with a trace2
    +-call so that users can make it visible if accessing submodule objects
    +-without an explicit repository still happens) or needs to be abandoned
    +-for whatever reason (in which case the migrated codepaths still retain
    +-their performance benefits).
    ++complete or needs to be abandoned for whatever reason (in which case the
    ++migrated codepaths still retain their performance benefits).
    + 
    + Naming Tests
    + ------------