[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(-)