Re: [PATCH 00/15] run-command API: pass functions & opts via struct

> This series changes the run-command API so that we pass options via a
> struct instead of via the argument list, the end result is that an API
> user looks like e.g.:
> 	
> 	+       const struct run_process_parallel_opts opts = {
> 	+               .tr2_category = "submodule",
> 	+               .tr2_label = "parallel/update",
> 	+
> 	+               .jobs = update_data->max_jobs,
> 	+
> 	+               .get_next_task = update_clone_get_next_task,
> 	+               .start_failure = update_clone_start_failure,
> 	+               .task_finished = update_clone_task_finished,
> 	+               .data = &suc,
> 	+       };
> 	[...]
> 	-       run_processes_parallel_tr2(suc.update_data->max_jobs, update_clone_get_next_task,
> 	-                                  update_clone_start_failure,
> 	-                                  update_clone_task_finished, &suc, "submodule",
> 	-                                  "parallel/update");
> 	+       run_processes_parallel(&opts);
> 

> These patches are derived from earlier patches I sent for passing the
> the "ungroup" parameter to this API[1], that's currently done with a
> global variable, because we needed a minimal change for a regression
> fix.
> 
> I'm submitting this now in the rc phase because there's another
> concurrent series that could make use of this[2]. The alternative
> would be for it to add an extra parameter to the two functions (one
> after this series).
> 
> The upcoming migration to the new hook API and config-based hooks[3]
> will also benefit significantly from this. I have a version of that
> topic rebased on top of this, having this first gets rid of a lot of
> churn, adding an optional callback just requires adding things to the
> struct introduced here, not changing every single caller.
> 
> (Passing) CI at:
> https://github.com/avar/git/tree/avar/hook-run-process-parallel-tty-regression-2-argument-passing
> 
> 1. https://lore.kernel.org/git/cover-v3-0.2-00000000000-20220527T090618Z-avarab@gmail.com/
> 2. https://lore.kernel.org/git/20220922232947.631309-1-calvinwan@google.com/
> 3. https://lore.kernel.org/git/cover-v5-00.36-00000000000-20210902T125110Z-avarab@gmail.com/
> 
> Brief commentary on individual patches below:
> 
> Ævar Arnfjörð Bjarmason (15):
>    hook tests: fix redirection logic error in 96e7225b310
>    submodule tests: reset "trace.out" between "grep" invocations
> 
> These bugfixes could be split out I suppose, but since we're changing
> this area 1/15 seemed prudent, 2/15 is required for a later test
> addition
> 
>    run-command tests: test stdout of run_command_parallel()
> 
> Tighten up tests, was ejected from the "ungroup" topic.
> 
>    run-command test helper: use "else if" pattern
>    run-command tests: use "return", not "exit"
> 
> Just setup for later changes.
> 
>    run-command API: have "run_processes_parallel{,_tr2}()" return void
> 
> Turns out we've never used the boilerplate return value for anything
> useful ever.
> 
>    run-command API: make "jobs" parameter an "unsigned int"
>    run-command API: don't fall back on online_cpus()
> 
> This allows us to make the "opts" struct "const", which helps a lot in
> passing it around later on.
> 
>    run-command.c: add an initializer for "struct parallel_processes"
>    run-command API: add nascent "struct run_process_parallel_opts"
>    run-command API: make run_process_parallel{,_tr2}() thin wrappers
>    run-command API: have run_process_parallel() take an "opts" struct
>    run-command API: move *_tr2() users to "run_processes_parallel()"
> 
> This is arguably one logical change (and at some point I had it as
> such), but as the diff would be really large I've tried to split this
> into easily digestable steps.
> 
>    run-command.c: don't copy *_fn to "struct parallel_processes"
>    run-command.c: don't copy "ungroup" to "struct parallel_processes"
> 
> The only reason for copying various parameters into "struct
> parallel_processes" was because we passed them as positionals, now
> that we have an "opts" struct we can just pass that along instead.
> 
> This leaves the "struct parallel_processes" in run-command.c purely
> for managing our own internal state.
> 
> By avoiding this copying we also cut down a lot on the boilerplate
> needed to add a new parameter.
> 
>   builtin/fetch.c             |  25 +++---
>   builtin/submodule--helper.c |  16 +++-
>   hook.c                      |  23 +++---
>   run-command.c               | 152 ++++++++++++++----------------------
>   run-command.h               |  71 ++++++++++++-----
>   submodule-config.c          |   2 +
>   submodule.c                 |  18 +++--
>   t/helper/test-run-command.c |  77 +++++++++++-------
>   t/t0061-run-command.sh      |  25 +++---
>   t/t1800-hook.sh             |   2 +-
>   t/t5526-fetch-submodules.sh |  16 +++-
>   11 files changed, 247 insertions(+), 180 deletions(-)
>