c549a40547
Allow the API callers to specify the number of jobs across which
hook execution can be parallelized. It defaults to 1 and no hook
currently changes it, so all hooks run sequentially as before.
This allows us to both pave the way for parallel hook execution
(that will be a follow-up patch series building upon this) and to
finish the API conversion of builtin/receive-pack.c, keeping the
output async sideband thread ("muxer") design as Peff suggested.
When .jobs==1 nothing changes, the "copy_to_sideband" async thread
still outputs directly via sideband channel 2, keeping the current
(mostly) real-time output characteristics, avoids unnecessary poll
delays or deadlock risks.
When .jobs > 1, a more complex muxer is needed to buffer the hook
output and avoid interleaving. After working on this mux I quickly
realized I was re-implementing run-command with ungroup=0 so that
idea was dropped in favor of run-command which outputs to stderr.
In other words, run-command itself already can buffer/deinterleave
pp child outputs (ungroup=0), so we can just connect its stderr to
the sideband async task when jobs > 1.
Maybe it helps to illustrate how it works with ascii graphics:
[ Sequential (jobs = 1) ] [ Parallel (jobs > 1) ]
+--------------+ +--------+ +--------+
| Hook Process | | Hook 1 | | Hook 2 |
+--------------+ +--------+ +--------+
| | |
| stderr (inherited) | stderr pipe |
| | (captured) |
v v v
+-------------------------------------------------------------+
| Parent Process |
| |
| (direct write) [run-command (buffered)] |
| | | |
| | | writes |
| v v |
| +-------------------------------------------+ |
| | stderr (FD 2) | |
| +-------------------------------------------+ |
| | |
| | (dup2'd to pipe) |
| v |
| +-----------------------+ |
| | sideband async thread | |
| +-----------------------+ |
+-------------------------------------------------------------+
When use_sideband == 0, the sideband async thread is missing, so
this same architecture just outputs via the parent stderr stream.
See the following commits for the hook API conversions doing this,
using pre-existing sideband thread logic from `copy_to_sideband`.
Suggested-by: Jeff King <peff@peff.net>
Signed-off-by: Adrian Ratiu <adrian.ratiu@collabora.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
Git - fast, scalable, distributed revision control system
Git is a fast, scalable, distributed revision control system with an unusually rich command set that provides both high-level operations and full access to internals.
Git is an Open Source project covered by the GNU General Public License version 2 (some parts of it are under different licenses, compatible with the GPLv2). It was originally written by Linus Torvalds with help of a group of hackers around the net.
Please read the file INSTALL for installation instructions.
Many Git online resources are accessible from https://git-scm.com/ including full documentation and Git related tools.
See Documentation/gittutorial.adoc to get started, then see
Documentation/giteveryday.adoc for a useful minimum set of commands, and
Documentation/git-<commandname>.adoc for documentation of each command.
If git has been correctly installed, then the tutorial can also be
read with man gittutorial or git help tutorial, and the
documentation of each command with man git-<commandname> or git help <commandname>.
CVS users may also want to read Documentation/gitcvs-migration.adoc
(man gitcvs-migration or git help cvs-migration if git is
installed).
The user discussion and development of Git take place on the Git mailing list -- everyone is welcome to post bug reports, feature requests, comments and patches to git@vger.kernel.org (read Documentation/SubmittingPatches for instructions on patch submission and Documentation/CodingGuidelines).
Those wishing to help with error message, usage and informational message
string translations (localization l10) should see po/README.md
(a po file is a Portable Object file that holds the translations).
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Issues which are security relevant should be disclosed privately to the Git Security mailing list git-security@googlegroups.com.
The maintainer frequently sends the "What's cooking" reports that list the current status of various development topics to the mailing list. The discussion following them give a good reference for project status, development direction and remaining tasks.
The name "git" was given by Linus Torvalds when he wrote the very first version. He described the tool as "the stupid content tracker" and the name as (depending on your mood):
- random three-letter combination that is pronounceable, and not actually used by any common UNIX command. The fact that it is a mispronunciation of "get" may or may not be relevant.
- stupid. contemptible and despicable. simple. Take your pick from the dictionary of slang.
- "global information tracker": you're in a good mood, and it actually works for you. Angels sing, and a light suddenly fills the room.
- "goddamn idiotic truckload of sh*t": when it breaks