gc/recursive-fetch-with-unused-submodules (was Re: What's cooking in git.git (Feb 2022, #05; Thu, 17))

> * gc/recursive-fetch-with-unused-submodules (2022-02-10) 8 commits
>  - submodule: fix bug and remove add_submodule_odb()
>  - fetch: fetch unpopulated, changed submodules
>  - submodule: extract get_fetch_task()
>  - t5526: use grep to assert on fetches
>  - t5526: introduce test helper to assert on fetches
>  - submodule: make static functions read submodules from commits
>  - submodule: store new submodule commits oid_array in a struct
>  - submodule: inline submodule_commits() into caller
>
>  When "git fetch --recurse-submodules" grabbed submodule commits
>  that would be needed to recursively check out newly fetched commits
>  in the superproject, it only paid attention to submodules that are
>  in the current checkout of the superproject.  We now do so for all
>  submodules that have been run "git submodule init" on.
>
>  Will merge to 'next'?
>  source: <20220210044152.78352-1-chooglen@google.com>