* ar/run-command-hook-take-2:
  receive-pack: convert receive hooks to hook API
  receive-pack: convert update hooks to new API
  run-command: poll child input in addition to output
  hook: add jobs option
  reference-transaction: use hook API instead of run-command
  transport: convert pre-push to hook API
  hook: allow separate std[out|err] streams
  hook: convert 'post-rewrite' hook in sequencer.c to hook API
  hook: provide stdin via callback
  run-command: add stdin callback for parallelization
  run-command: add helper for pp child states
  t1800: add hook output stream tests

Some hooks use opaque structs to keep internal state between callbacks.

Because hooks ran sequentially (jobs == 1) with one command per hook,
these internal states could be allocated on the stack for each hook run.

Next commits add the ability to run multiple commands for each hook, so
the states cannot be shared or stored on the stack anymore, especially
since down the line we will also enable parallel execution (jobs > 1).

Add alloc/free helpers for each hook, doing a "deep" alloc/init & free
of their internal opaque struct.

The alloc callback takes a context pointer, to initialize the struct at
at the time of resource acquisition.

These callbacks must always be provided together: no alloc without free
and no free without alloc, otherwise a BUG() is triggered.

Signed-off-by: Adrian Ratiu <adrian.ratiu@collabora.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

Hooks are limited to run one command (the default from the hookdir) for
each event. This limitation makes it impossible to run multiple commands
via config files, which the next commits will add.

Implement the ability to run a list of hooks in hook.[ch]. For now, the
list contains only one entry representing the "default" hook from the
hookdir, so there is no user-visible change in this commit.

All hook commands still run sequentially like before. A separate patch
series will enable running them in parallel.

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>

The previous commit introduced an ability to run multiple commands for
hook events and next commit will introduce the ability to define hooks
from configs, in addition to the "traditional" hooks from the hookdir.

Introduce a new command "git hook list" to make inspecting hooks easier
both for users and for the tests we will add.

Further commits will expand on this, e.g. by adding a -z output mode.

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>

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>

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>

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>

Since hooks can now be supplied via the config, and a config can be
present without a gitdir via the global and system configs, we can start
to allow 'git hook run' to occur without a gitdir. This enables us to do
things like run sendemail-validate hooks when running 'git send-email'
from a nongit directory.

It still doesn't make sense to look for hooks in the hookdir in nongit
repos, though, as there is no hookdir.

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>

Add a NUL-terminate mode to git hook list, just in case hooks are
configured with weird characters like newlines in their names.

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>

* ar/run-command-hook-take-2:
  builtin/receive-pack: avoid spinning no-op sideband async threads