Subject: [PATCH v6 07/11] hook: allow overriding the ungroup option

From: Adrian Ratiu <[email-masked]>
Date: Fri, 26 Dec 2025 14:23:30 +0200

When calling run_process_parallel() in run_hooks_opt(), the
ungroup option is currently hardcoded to .ungroup = 1.

This causes problems when ungrouping should be disabled, for
example when sideband-reading collated output from child hooks,
because sideband-reading and ungrouping are mutually exclusive.

Thus a new hook.h option is added to allow overriding.

The existing ungroup=1 behavior is preserved in the run_hooks()
API and the "hook run" command. We could modify these to take
an option if necessary, so I added two code comments there.

Signed-off-by: Adrian Ratiu <[email-masked]>
---
 builtin/hook.c | 6 ++++++
 commit.c       | 3 +++
 hook.c         | 5 ++++-
 hook.h         | 5 +++++
 4 files changed, 18 insertions(+), 1 deletion(-)

diff --git a/builtin/hook.c b/builtin/hook.c
index 7afec380d2..73e7b8c2e8 100644
--- a/builtin/hook.c
+++ b/builtin/hook.c
@@ -43,6 +43,12 @@ static int run(int argc, const char **argv, const char *prefix,
 	if (!argc)
 		goto usage;
 
+	/*
+	 * All current "hook run" use-cases require ungrouped child output.
+	 * If this changes, a hook run argument can be added to toggle it.
+	 */
+	opt.ungroup = 1;
+
 	/*
 	 * Having a -- for "run" when providing <hook-args> is
 	 * mandatory.
diff --git a/commit.c b/commit.c
index 709c9eed58..2527f15d9d 100644
--- a/commit.c
+++ b/commit.c
@@ -1978,6 +1978,9 @@ int run_commit_hook(int editor_is_used, const char *index_file,
 		strvec_push(&opt.args, arg);
 	va_end(args);
 
+	/* All commit hook use-cases require ungrouping child output. */
+	opt.ungroup = 1;
+
 	opt.invoked_hook = invoked_hook;
 	return run_hooks_opt(the_repository, name, &opt);
 }
diff --git a/hook.c b/hook.c
index 5ddd7678d1..00a1e2ad22 100644
--- a/hook.c
+++ b/hook.c
@@ -153,7 +153,7 @@ int run_hooks_opt(struct repository *r, const char *hook_name,
 		.tr2_label = hook_name,
 
 		.processes = 1,
-		.ungroup = 1,
+		.ungroup = options->ungroup,
 
 		.get_next_task = pick_next_hook,
 		.start_failure = notify_start_failure,
@@ -198,6 +198,9 @@ int run_hooks(struct repository *r, const char *hook_name)
 {
 	struct run_hooks_opt opt = RUN_HOOKS_OPT_INIT;
 
+	/* All use-cases of this API require ungrouping. */
+	opt.ungroup = 1;
+
 	return run_hooks_opt(r, hook_name, &opt);
 }
 
diff --git a/hook.h b/hook.h
index 2169d4a6bd..78a1a44690 100644
--- a/hook.h
+++ b/hook.h
@@ -34,6 +34,11 @@ struct run_hooks_opt
 	 */
 	int *invoked_hook;
 
+	/**
+	 * Allow hooks to set run_processes_parallel() 'ungroup' behavior.
+	 */
+	unsigned int ungroup:1;
+
 	/**
 	 * Path to file which should be piped to stdin for each hook.
 	 */
-- 
2.51.2