Add a new config `hook.forceStdoutToStderr` which allows enabling
extensions.hookStdoutToStderr by default at runtime, both for new
and existing repositories.
This makes it easier for users to enable hook parallelization for
hooks like pre-push by enforcing output consistency. See previous
commit for a more in-depth explanation & alternatives considered.
Signed-off-by: Adrian Ratiu <adrian.ratiu@collabora.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
All hooks already redirect stdout to stderr with the exception of
pre-push which has a known user who depends on the separate stdout
versus stderr outputs (the git-lfs project).
The pre-push behavior was a surprise which we found out about after
causing a regression for git-lfs. Notably, it might not be the only
exception (it's the one we know about). There might be more.
This presents a challenge because stdout_to_stderr is required for
hook parallelization, so run-command can buffer and de-interleave
the hook outputs using ungroup=0, when hook.jobs > 1.
Introduce an extension to enforce consistency: all hooks merge stdout
into stderr and can be safely parallelized. This provides a clean
separation and avoids breaking existing stdout vs stderr behavior.
When this extension is disabled, the `hook.jobs` config has no
effect for pre-push, to prevent garbled (interleaved) parallel
output, so it runs sequentially like before.
Alternatives I've considered to this extension include:
1. Allowing pre-push to run in parallel with interleaved output.
2. Always running pre-push sequentially (no parallel jobs for it).
3. Making users (only git-lfs? maybe more?) fix their hooks to read
stderr not stdout.
Out of all these alternatives, I think this extension is the most
reasonable compromise, to not break existing users, allow pre-push
parallel jobs for those who need it (with correct outputs) and also
future-proofing in case there are any more exceptions to be added.
Signed-off-by: Adrian Ratiu <adrian.ratiu@collabora.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
Add a hook.<event>.jobs count config that allows users to override the
global hook.jobs setting for specific hook events.
This allows finer-grained control over parallelism on a per-event basis.
For example, to run `post-receive` hooks with up to 4 parallel jobs
while keeping other events at their global default:
[hook]
post-receive.jobs = 4
Signed-off-by: Adrian Ratiu <adrian.ratiu@collabora.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
Several hooks are known to be inherently non-parallelizable, so initialize
them with RUN_HOOKS_OPT_INIT_FORCE_SERIAL. This pins jobs=1 and overrides
any hook.jobs or runtime -j flags.
These hooks are:
applypatch-msg, pre-commit, prepare-commit-msg, commit-msg, post-commit,
post-checkout, and push-to-checkout.
Signed-off-by: Emily Shaffer <emilyshaffer@google.com>
Signed-off-by: Adrian Ratiu <adrian.ratiu@collabora.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
Hooks always run in sequential order due to the hardcoded jobs == 1
passed to run_process_parallel(). Remove that hardcoding to allow
users to run hooks in parallel (opt-in).
Users need to decide which hooks to run in parallel, by specifying
"parallel = true" in the config, because git cannot know if their
specific hooks are safe to run or not in parallel (for e.g. two hooks
might write to the same file or call the same program).
Some hooks are unsafe to run in parallel by design: these will marked
in the next commit using RUN_HOOKS_OPT_INIT_FORCE_SERIAL.
The hook.jobs config specifies the default number of jobs applied to all
hooks which have parallelism enabled.
Signed-off-by: Emily Shaffer <emilyshaffer@google.com>
Helped-by: Ævar Arnfjörð Bjarmason <avarab@gmail.com>
Signed-off-by: Adrian Ratiu <adrian.ratiu@collabora.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
The hook.jobs config is a global way to set hook parallelization for
all hooks, in the sense that it is not per-event nor per-hook.
Finer-grained configs will be added in later commits which can override
it, for e.g. via a per-event type job options. Next commits will also
add to this item's documentation.
Parse hook.jobs config key in hook_config_lookup_all() and store its
value in hook_all_config_cb.jobs, then transfer it into
hook_config_cache.jobs after the config pass completes.
This is mostly plumbing and the cached value is not yet used.
Signed-off-by: Adrian Ratiu <adrian.ratiu@collabora.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
Add the ability for empty events to clear previously set multivalue
variables, so the newly added "hook.*.event" behave like the other
multivalued keys.
Suggested-by: Patrick Steinhardt <ps@pks.im>
Signed-off-by: Adrian Ratiu <adrian.ratiu@collabora.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
Hooks specified via configs are always enabled, however users
might want to disable them without removing from the config,
like locally disabling a global hook.
Add a hook.<name>.enabled config which defaults to true and
can be optionally set for each configured hook.
Suggested-by: Patrick Steinhardt <ps@pks.im>
Signed-off-by: Adrian Ratiu <adrian.ratiu@collabora.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
Teach the hook.[hc] library to parse configs to populate the list of
hooks to run for a given event.
Multiple commands can be specified for a given hook by providing
"hook.<friendly-name>.command = <path-to-hook>" and
"hook.<friendly-name>.event = <hook-event>" lines.
Hooks will be started in config order of the "hook.<name>.event"
lines and will be run sequentially (.jobs == 1) like before.
Running the hooks in parallel will be enabled in a future patch.
The "traditional" hook from the hookdir is run last, if present.
A strmap cache is added to struct repository to avoid re-reading
the configs on each rook run. This is useful for hooks like the
ref-transaction which gets executed multiple times per process.
Examples:
$ git config --get-regexp "^hook\."
hook.bar.command=~/bar.sh
hook.bar.event=pre-commit
# Will run ~/bar.sh, then .git/hooks/pre-commit
$ git hook run pre-commit
Signed-off-by: Emily Shaffer <emilyshaffer@google.com>
Signed-off-by: Adrian Ratiu <adrian.ratiu@collabora.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
