hook: allow pre-push parallel execution
pre-push is the only hook that keeps stdout and stderr separate (for backwards compatibility with git-lfs and potentially other users). This prevents parallelizing it because run-command needs stdout_to_stderr=1 to buffer and de-interleave parallel outputs. Since we now default to jobs=1, backwards compatibility is maintained without needing any extension or extra config: when no parallelism is requested, pre-push behaves exactly as before. When the user explicitly opts into parallelism via hook.jobs > 1, hook.<event>.jobs > 1, or -jN, they accept the changed output behavior. Document this and let get_hook_jobs() set stdout_to_stderr=1 automatically when jobs > 1, removing the need for any extension infrastructure. Signed-off-by: Adrian Ratiu <adrian.ratiu@collabora.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>
Adrian Ratiu committed
Apr 10, 2026 at 12:06 UTC
f776b77f0032fb342d567156626ef3fe9586443f
5 files changed
+60
-12
Documentation/config/hook.adoc
+4
index 21800db648..94c7a9808e 100644
--- a/Documentation/config/hook.adoc
+++ b/Documentation/config/hook.adoc
@@ -39,3 +39,7 @@ hook.jobs::
+
This setting has no effect unless all configured hooks for the event have
`hook.<friendly-name>.parallel` set to `true`.
++
+For `pre-push` hooks, which normally keep stdout and stderr separate,
+setting this to a value greater than 1 (or passing `-j`) will merge stdout
+into stderr to allow correct de-interleaving of parallel output.
hook.c
+16
-8
index 85c0de5e47..25762b6c8d 100644
--- a/hook.c
+++ b/hook.c
@@ -555,18 +555,24 @@ static void run_hooks_opt_clear(struct run_hooks_opt *options)
strvec_clear(&options->args);
}
+/*
+ * When running in parallel, stdout must be merged into stderr so
+ * run-command can buffer and de-interleave outputs correctly. This
+ * applies even to hooks like pre-push that normally keep stdout and
+ * stderr separate: the user has opted into parallelism, so the output
+ * stream behavior changes accordingly.
+ */
+static void merge_output_if_parallel(struct run_hooks_opt *options)
+{
+ if (options->jobs > 1)
+ options->stdout_to_stderr = 1;
+}
+
/* Determine how many jobs to use for hook execution. */
static unsigned int get_hook_jobs(struct repository *r,
struct run_hooks_opt *options,
struct string_list *hook_list)
{
- /*
- * Hooks needing separate output streams must run sequentially.
- * Next commit will allow parallelizing these as well.
- */
- if (!options->stdout_to_stderr)
- return 1;
-
/*
* An explicit job count overrides everything else: this covers both
* FORCE_SERIAL callers (for hooks that must never run in parallel)
@@ -575,7 +581,7 @@ static unsigned int get_hook_jobs(struct repository *r,
* aggressively than the default.
*/
if (options->jobs)
- return options->jobs;
+ goto cleanup;
/*
* Use hook.jobs from the already-parsed config cache (in-repo), or
@@ -603,6 +609,8 @@ static unsigned int get_hook_jobs(struct repository *r,
}
}
+cleanup:
+ merge_output_if_parallel(options);
return options->jobs;
}
hook.h
+4
-2
index ba7056f872..01db4226a6 100644
--- a/hook.h
+++ b/hook.h
@@ -106,8 +106,10 @@ struct run_hooks_opt {
* Send the hook's stdout to stderr.
*
* This is the default behavior for all hooks except pre-push,
- * which has separate stdout and stderr streams for backwards
- * compatibility reasons.
+ * which keeps stdout and stderr separate for backwards compatibility.
+ * When parallel execution is requested (jobs > 1), get_hook_jobs()
+ * overrides this to 1 for all hooks so run-command can de-interleave
+ * their outputs correctly.
*/
unsigned int stdout_to_stderr:1;
t/t1800-hook.sh
+32
index a3011a01ca..4a978aff5e 100755
--- a/t/t1800-hook.sh
+++ b/t/t1800-hook.sh
@@ -800,4 +800,36 @@ test_expect_success 'one non-parallel hook forces the whole event to run seriall
test_cmp expect hook.order
'
+test_expect_success 'client hooks: pre-push parallel execution merges stdout to stderr' '
+ test_when_finished "rm -rf remote-par stdout.actual stderr.actual" &&
+ git init --bare remote-par &&
+ git remote add origin-par remote-par &&
+ test_commit par-commit &&
+ mkdir -p .git/hooks &&
+ setup_hooks pre-push &&
+ test_config hook.jobs 2 &&
+ git push origin-par HEAD:main >stdout.actual 2>stderr.actual &&
+ check_stdout_merged_to_stderr pre-push
+'
+
+test_expect_success 'client hooks: pre-push runs in parallel when hook.jobs > 1' '
+ test_when_finished "rm -rf repo-parallel remote-parallel" &&
+ git init --bare remote-parallel &&
+ git init repo-parallel &&
+ git -C repo-parallel remote add origin ../remote-parallel &&
+ test_commit -C repo-parallel A &&
+
+ write_sentinel_hook repo-parallel/.git/hooks/pre-push &&
+ git -C repo-parallel config hook.hook-2.event pre-push &&
+ git -C repo-parallel config hook.hook-2.command \
+ "$(sentinel_detector sentinel hook.order)" &&
+ git -C repo-parallel config hook.hook-2.parallel true &&
+
+ git -C repo-parallel config hook.jobs 2 &&
+
+ git -C repo-parallel push origin HEAD >out 2>err &&
+ echo parallel >expect &&
+ test_cmp expect repo-parallel/hook.order
+'
+
test_done
transport.c
+4
-2
index e53936d87b..9406ec4f2d 100644
--- a/transport.c
+++ b/transport.c
@@ -1391,8 +1391,10 @@ static int run_pre_push_hook(struct transport *transport,
opt.feed_pipe_cb_data_free = pre_push_hook_data_free;
/*
- * pre-push hooks expect stdout & stderr to be separate, so don't merge
- * them to keep backwards compatibility with existing hooks.
+ * pre-push hooks keep stdout and stderr separate by default for
+ * backwards compatibility. When the user opts into parallel execution
+ * via hook.jobs > 1 or -j, get_hook_jobs() will set stdout_to_stderr=1
+ * automatically so run-command can de-interleave the outputs.
*/
opt.stdout_to_stderr = 0;