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
@@ -39,3 +39,7 @@ hook.jobs::
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+
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This setting has no effect unless all configured hooks for the event have
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`hook.<friendly-name>.parallel` set to `true`.
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++
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+For `pre-push` hooks, which normally keep stdout and stderr separate,
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+setting this to a value greater than 1 (or passing `-j`) will merge stdout
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+into stderr to allow correct de-interleaving of parallel output.
hook.c
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-8
@@ -555,18 +555,24 @@ static void run_hooks_opt_clear(struct run_hooks_opt *options)
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strvec_clear(&options->args);
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}
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+/*
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+ * When running in parallel, stdout must be merged into stderr so
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+ * run-command can buffer and de-interleave outputs correctly. This
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+ * applies even to hooks like pre-push that normally keep stdout and
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+ * stderr separate: the user has opted into parallelism, so the output
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+ * stream behavior changes accordingly.
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+ */
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+static void merge_output_if_parallel(struct run_hooks_opt *options)
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+{
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+ if (options->jobs > 1)
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+ options->stdout_to_stderr = 1;
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+}
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+
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/* Determine how many jobs to use for hook execution. */
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static unsigned int get_hook_jobs(struct repository *r,
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struct run_hooks_opt *options,
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struct string_list *hook_list)
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{
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- /*
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- * Hooks needing separate output streams must run sequentially.
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- * Next commit will allow parallelizing these as well.
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- */
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- if (!options->stdout_to_stderr)
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- return 1;
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-
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/*
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* An explicit job count overrides everything else: this covers both
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* FORCE_SERIAL callers (for hooks that must never run in parallel)
@@ -575,7 +581,7 @@ static unsigned int get_hook_jobs(struct repository *r,
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* aggressively than the default.
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*/
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if (options->jobs)
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- return options->jobs;
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+ goto cleanup;
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/*
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* 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,
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}
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}
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+cleanup:
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+ merge_output_if_parallel(options);
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return options->jobs;
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}
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hook.h
+4
-2
@@ -106,8 +106,10 @@ struct run_hooks_opt {
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* Send the hook's stdout to stderr.
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*
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* This is the default behavior for all hooks except pre-push,
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- * which has separate stdout and stderr streams for backwards
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- * compatibility reasons.
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+ * which keeps stdout and stderr separate for backwards compatibility.
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+ * When parallel execution is requested (jobs > 1), get_hook_jobs()
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+ * overrides this to 1 for all hooks so run-command can de-interleave
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+ * their outputs correctly.
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*/
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unsigned int stdout_to_stderr:1;
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t/t1800-hook.sh
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@@ -800,4 +800,36 @@ test_expect_success 'one non-parallel hook forces the whole event to run seriall
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test_cmp expect hook.order
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'
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+test_expect_success 'client hooks: pre-push parallel execution merges stdout to stderr' '
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+ test_when_finished "rm -rf remote-par stdout.actual stderr.actual" &&
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+ git init --bare remote-par &&
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+ git remote add origin-par remote-par &&
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+ test_commit par-commit &&
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+ mkdir -p .git/hooks &&
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+ setup_hooks pre-push &&
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+ test_config hook.jobs 2 &&
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+ git push origin-par HEAD:main >stdout.actual 2>stderr.actual &&
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+ check_stdout_merged_to_stderr pre-push
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+'
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+
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+test_expect_success 'client hooks: pre-push runs in parallel when hook.jobs > 1' '
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+ test_when_finished "rm -rf repo-parallel remote-parallel" &&
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+ git init --bare remote-parallel &&
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+ git init repo-parallel &&
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+ git -C repo-parallel remote add origin ../remote-parallel &&
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+ test_commit -C repo-parallel A &&
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+
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+ write_sentinel_hook repo-parallel/.git/hooks/pre-push &&
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+ git -C repo-parallel config hook.hook-2.event pre-push &&
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+ git -C repo-parallel config hook.hook-2.command \
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+ "$(sentinel_detector sentinel hook.order)" &&
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+ git -C repo-parallel config hook.hook-2.parallel true &&
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+
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+ git -C repo-parallel config hook.jobs 2 &&
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+
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+ git -C repo-parallel push origin HEAD >out 2>err &&
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+ echo parallel >expect &&
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+ test_cmp expect repo-parallel/hook.order
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+'
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+
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test_done
transport.c
+4
-2
@@ -1391,8 +1391,10 @@ static int run_pre_push_hook(struct transport *transport,
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opt.feed_pipe_cb_data_free = pre_push_hook_data_free;
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/*
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- * pre-push hooks expect stdout & stderr to be separate, so don't merge
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- * them to keep backwards compatibility with existing hooks.
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+ * pre-push hooks keep stdout and stderr separate by default for
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+ * backwards compatibility. When the user opts into parallel execution
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+ * via hook.jobs > 1 or -j, get_hook_jobs() will set stdout_to_stderr=1
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+ * automatically so run-command can de-interleave the outputs.
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*/
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opt.stdout_to_stderr = 0;
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