Johannes Schindelin 049f0cf1a5 GIT-VERSION-GEN: allow it to be run in parallel
"Why would one want to run it in parallel?" I hear you ask. I am glad
you are curious, because a curious story is what it is, indeed.

The `GIT-VERSION-GEN` script is quite a pillar of Git's source code,
with most lines being unchanged for the past 15 years. Until the v2.48.0
release candidate cycle.

Its original purpose was to generate the version string and store it in
the `GIT-VERSION-FILE`.

This paradigm changed quite dramatically when support for building with
Meson was introduced. Most crucially, a38edab7c88b (Makefile: generate
doc versions via GIT-VERSION-GEN, 2024-12-06) changed the way the
documentation is built by using the `GIT-VERSION-GEN` file to write out
the `asciidocor-extensions.rb` and `asciidoc.conf` files with now
hard-coded version strings.

Crucially, the Makefile rule to generate those files need to be run
in every build because `GIT_VERSION` could have been specified, which
would require these files to be changed.

This introduced a surprising race condition!

And this is how that race surfaces: When calling `make -j2 html man`
from the top-level directory (a variant of which is invoked in Git for
Windows' release process), two sub-processes are spawned, a `make -C
Documentation html` one and a `make -C Documentation man` one. Both run
the rule to (re-)generate `asciidoctor-extensions.rb` or
`asciidoc.conf`, invoking `GIT-VERSION-GEN` to do so. That script first
generates a temporary file (appending the `+` character to the
filename), then looks whether it contains something different than the
already existing file (if it exists, that is), and either replaces it if
needed, or removes the temporary file. If one of the two parallel
invocations removes that temporary file before the other can compare it,
or even worse: if one tries to replace the target file just after the
other _started_ writing the temporary file (but did not finish), that
race condition now causes bad builds.

This may sound highly theoretical, but due to Git's choices, Git for
Windows is forced to use a (slow) POSIX emulation layer to run that
script and in the blink of an eye it becomes very much not theoretical
at all. See these failed GitHub workflow runs as Exhibit A:

https://github.com/git-for-windows/git-sdk-32/actions/runs/12663456654
https://github.com/git-for-windows/git-sdk-32/actions/runs/12683174970
https://github.com/git-for-windows/git-sdk-64/actions/runs/12649348496

While it is undesirable to run this script over and over again,
certainly when this involves above-mentioned slow POSIX emulation layer,
the stage of the release cycle in which we are presently finding
ourselves dictates that a quick and reliable work-around be implemented
that works around the race condition without changing the overall
architecture of the build process.

This patch does that: By using a filename suffix for the temporary file
that includes the currently-executing script's process ID, We guarantee
that the two competing invocations cannot overwrite or remove each
others' temporary files.

Incidentally, this also fixes something else: The `+` character is
not even a valid filename character on Windows. The only reason why Git
for Windows did not need this is that above-mentioned POSIX emulation
layer also plays a couple of tricks with filenames (tricks that are not
interoperable with regular Windows programs, though), and previous
attempts to remedy this in git/git were unsuccessful, see e.g.
https://lore.kernel.org/git/pull.216.git.gitgitgadget@gmail.com/

This commit fixes one of the issues that are currently delaying Git for
Windows v2.48.0-rc2.

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
2025-01-09 12:40:38 +01:00
2025-01-07 16:57:08 +01:00
2024-12-15 17:54:33 -08:00
2024-09-20 14:40:41 -07:00
2024-12-23 09:32:25 -08:00
2024-09-06 09:31:15 -07:00
2024-12-23 09:32:11 -08:00
2024-09-23 10:35:07 -07:00
2025-01-07 16:56:21 +01:00
2024-12-23 09:32:11 -08:00
2024-09-16 10:46:00 -07:00
2024-12-23 09:32:11 -08:00
2024-08-23 09:02:33 -07:00
2024-12-23 09:32:11 -08:00
2024-12-23 09:32:11 -08:00
2025-01-07 16:56:21 +01:00
2024-10-23 16:16:36 -04:00
2024-10-23 16:16:36 -04:00
2024-10-23 16:16:36 -04:00
2024-09-19 13:46:00 -07:00
2025-01-07 16:56:21 +01:00
2024-10-23 16:16:36 -04:00
2025-01-07 16:56:21 +01:00
2024-12-23 09:32:11 -08:00
2024-10-21 16:05:04 -04:00
2025-01-07 16:56:21 +01:00
2025-01-07 12:36:04 +01:00
2024-09-19 13:46:01 -07:00
2024-12-23 09:32:29 -08:00
2024-12-23 09:32:29 -08:00
2024-11-20 14:43:30 +09:00
2024-09-19 13:46:12 -07:00
2024-09-30 11:23:03 -07:00
2024-12-03 12:38:49 +09:00
2024-12-23 09:32:11 -08:00
2024-12-23 09:32:11 -08:00
2024-12-23 09:32:11 -08:00
2024-09-04 08:03:24 -07:00

Git for Windows

Contributor Covenant Open in Visual Studio Code Build status Join the chat at https://gitter.im/git-for-windows/git

This is Git for Windows, the Windows port of Git.

The Git for Windows project is run using a governance model. If you encounter problems, you can report them as GitHub issues, discuss them on Git for Windows' Google Group, and contribute bug fixes.

To build Git for Windows, please either install Git for Windows' SDK, start its git-bash.exe, cd to your Git worktree and run make, or open the Git worktree as a folder in Visual Studio.

To verify that your build works, use one of the following methods:

  • If you want to test the built executables within Git for Windows' SDK, prepend <worktree>/bin-wrappers to the PATH.

  • Alternatively, run make install in the Git worktree.

  • If you need to test this in a full installer, run sdk build git-and-installer.

  • You can also "install" Git into an existing portable Git via make install DESTDIR=<dir> where <dir> refers to the top-level directory of the portable Git. In this instance, you will want to prepend that portable Git's /cmd directory to the PATH, or test by running that portable Git's git-bash.exe or git-cmd.exe.

  • If you built using a recent Visual Studio, you can use the menu item Build>Install git (you will want to click on Project>CMake Settings for Git first, then click on Edit JSON and then point installRoot to the mingw64 directory of an already-unpacked portable Git).

    As in the previous bullet point, you will then prepend /cmd to the PATH or run using the portable Git's git-bash.exe or git-cmd.exe.

  • If you want to run the built executables in-place, but in a CMD instead of inside a Bash, you can run a snippet like this in the git-bash.exe window where Git was built (ensure that the EOF line has no leading spaces), and then paste into the CMD window what was put in the clipboard:

    clip.exe <<EOF
    set GIT_EXEC_PATH=$(cygpath -aw .)
    set PATH=$(cygpath -awp ".:contrib/scalar:/mingw64/bin:/usr/bin:$PATH")
    set GIT_TEMPLATE_DIR=$(cygpath -aw templates/blt)
    set GITPERLLIB=$(cygpath -aw perl/build/lib)
    EOF
    
  • If you want to run the built executables in-place, but outside of Git for Windows' SDK, and without an option to set/override any environment variables (e.g. in Visual Studio's debugger), you can call the Git executable by its absolute path and use the --exec-path option, like so:

    C:\git-sdk-64\usr\src\git\git.exe --exec-path=C:\git-sdk-64\usr\src\git help
    

    Note: for this to work, you have to hard-link (or copy) the .dll files from the /mingw64/bin directory to the Git worktree, or add the /mingw64/bin directory to the PATH somehow or other.

To make sure that you are testing the correct binary, call ./git.exe version in the Git worktree, and then call git version in a directory/window where you want to test Git, and verify that they refer to the same version (you may even want to pass the command-line option --build-options to look at the exact commit from which the Git version was built).

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.txt to get started, then see Documentation/giteveryday.txt for a useful minimum set of commands, and Documentation/git-<commandname>.txt 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.txt (man gitcvs-migration or git help cvs-migration if git is installed).

The user discussion and development of core 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).

To subscribe to the list, send an email to git+subscribe@vger.kernel.org (see https://subspace.kernel.org/subscribing.html for details). The mailing list archives are available at https://lore.kernel.org/git/, https://marc.info/?l=git and other archival sites. The core git mailing list is plain text (no HTML!).

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
Description
A fork of Git containing Windows-specific patches.
Readme 414 MiB
2025-08-19 03:50:05 -05:00
Languages
C 51.7%
Shell 37.5%
Perl 4.3%
Tcl 3%
Python 0.8%
Other 2.5%