run-command API: have "run_processes_parallel{,_tr2}()" return void

Change the "run_processes_parallel{,_tr2}()" functions to return void,
instead of int. Ever since c553c72eed (run-command: add an
asynchronous parallel child processor, 2015-12-15) they have
unconditionally returned 0.

To get a "real" return value out of this function the caller needs to
get it via the "task_finished_fn" callback, see the example in hook.c
added in 96e7225b31 (hook: add 'run' subcommand, 2021-12-22).

So the "result = " and "if (!result)" code added to "builtin/fetch.c"
d54dea77db (fetch: let --jobs=<n> parallelize --multiple, too,
2019-10-05) has always been redundant, we always took that "if"
path. Likewise the "ret =" in "t/helper/test-run-command.c" added in
be5d88e112 (test-tool run-command: learn to run (parts of) the
testsuite, 2019-10-04) wasn't used, instead we got the return value
from the "if (suite.failed.nr > 0)" block seen in the context.

Subsequent commits will alter this API interface, getting rid of this
always-zero return value makes it easier to understand those changes.

Signed-off-by: Ævar Arnfjörð Bjarmason <avarab@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

builtin/fetch.c

@@ -1953,15 +1953,14 @@ static int fetch_multiple(struct string_list *list, int max_children)
 		struct parallel_fetch_state state = { argv.v, list, 0, 0 };
 
 		strvec_push(&argv, "--end-of-options");
-		result = run_processes_parallel_tr2(max_children,
-						    &fetch_next_remote,
-						    &fetch_failed_to_start,
-						    &fetch_finished,
-						    &state,
-						    "fetch", "parallel/fetch");
+		run_processes_parallel_tr2(max_children,
+					   &fetch_next_remote,
+					   &fetch_failed_to_start,
+					   &fetch_finished,
+					   &state,
+					   "fetch", "parallel/fetch");
 
-		if (!result)
-			result = state.result;
+		result = state.result;
 	} else
 		for (i = 0; i < list->nr; i++) {
 			const char *name = list->items[i].string;

run-command.c

@@ -1783,11 +1783,11 @@ static int pp_collect_finished(struct parallel_processes *pp)
 	return result;
 }
 
-int run_processes_parallel(int n,
-			   get_next_task_fn get_next_task,
-			   start_failure_fn start_failure,
-			   task_finished_fn task_finished,
-			   void *pp_cb)
+void run_processes_parallel(int n,
+			    get_next_task_fn get_next_task,
+			    start_failure_fn start_failure,
+			    task_finished_fn task_finished,
+			    void *pp_cb)
 {
 	int i, code;
 	int output_timeout = 100;
@@ -1834,25 +1834,20 @@ int run_processes_parallel(int n,
 	}
 
 	pp_cleanup(&pp);
-	return 0;
 }
 
-int run_processes_parallel_tr2(int n, get_next_task_fn get_next_task,
-			       start_failure_fn start_failure,
-			       task_finished_fn task_finished, void *pp_cb,
-			       const char *tr2_category, const char *tr2_label)
+void run_processes_parallel_tr2(int n, get_next_task_fn get_next_task,
+				start_failure_fn start_failure,
+				task_finished_fn task_finished, void *pp_cb,
+				const char *tr2_category, const char *tr2_label)
 {
-	int result;
-
 	trace2_region_enter_printf(tr2_category, tr2_label, NULL, "max:%d",
 				   ((n < 1) ? online_cpus() : n));
 
-	result = run_processes_parallel(n, get_next_task, start_failure,
-					task_finished, pp_cb);
+	run_processes_parallel(n, get_next_task, start_failure,
+			       task_finished, pp_cb);
 
 	trace2_region_leave(tr2_category, tr2_label, NULL);
-
-	return result;
 }
 
 int run_auto_maintenance(int quiet)

run-command.h

@@ -485,14 +485,14 @@ typedef int (*task_finished_fn)(int result,
  * API reads that setting.
  */
 extern int run_processes_parallel_ungroup;
-int run_processes_parallel(int n,
-			   get_next_task_fn,
-			   start_failure_fn,
-			   task_finished_fn,
-			   void *pp_cb);
-int run_processes_parallel_tr2(int n, get_next_task_fn, start_failure_fn,
-			       task_finished_fn, void *pp_cb,
-			       const char *tr2_category, const char *tr2_label);
+void run_processes_parallel(int n,
+			    get_next_task_fn,
+			    start_failure_fn,
+			    task_finished_fn,
+			    void *pp_cb);
+void run_processes_parallel_tr2(int n, get_next_task_fn, start_failure_fn,
+				task_finished_fn, void *pp_cb,
+				const char *tr2_category, const char *tr2_label);
 
 /**
  * Convenience function which prepares env for a command to be run in a

t/helper/test-run-command.c

@@ -192,8 +192,8 @@ static int testsuite(int argc, const char **argv)
 	fprintf(stderr, "Running %"PRIuMAX" tests (%d at a time)\n",
 		(uintmax_t)suite.tests.nr, max_jobs);
 
-	ret = run_processes_parallel(max_jobs, next_test, test_failed,
-				     test_finished, &suite);
+	run_processes_parallel(max_jobs, next_test, test_failed,
+			       test_finished, &suite);
 
 	if (suite.failed.nr > 0) {
 		ret = 1;
@@ -428,16 +428,16 @@ int cmd__run_command(int argc, const char **argv)
 	strvec_pushv(&proc.args, (const char **)argv + 3);
 
 	if (!strcmp(argv[1], "run-command-parallel")) {
-		exit(run_processes_parallel(jobs, parallel_next,
-					    NULL, NULL, &proc));
+		run_processes_parallel(jobs, parallel_next, NULL, NULL, &proc);
 	} else if (!strcmp(argv[1], "run-command-abort")) {
-		exit(run_processes_parallel(jobs, parallel_next,
-					    NULL, task_finished, &proc));
+		run_processes_parallel(jobs, parallel_next, NULL,
+				       task_finished, &proc);
 	} else if (!strcmp(argv[1], "run-command-no-jobs")) {
-		exit(run_processes_parallel(jobs, no_job,
-					    NULL, task_finished, &proc));
+		run_processes_parallel(jobs, no_job, NULL, task_finished,
+				       &proc);
 	} else {
 		fprintf(stderr, "check usage\n");
 		return 1;
 	}
+	exit(0);
 }