libgit2 - the Git linkable library

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libgit2 is a portable, pure C implementation of the Git core methodsprovided as a linkable library with a solid API, allowing to build Gitfunctionality into your application. Language bindings likeRugged (Ruby),LibGit2Sharp (.NET),pygit2 (Python) andNodeGit (Node) allow you to build Git toolingin your favorite language.

libgit2 is used to power Git GUI clients likeGitKraken and gmasterand on Git hosting providers like GitHub,GitLab andAzure DevOps.We perform the merge every time you click "merge pull request".

libgit2 is licensed under a very permissive license (GPLv2 with a specialLinking Exception). This basically means that you can link it (unmodified)with any kind of software without having to release its source code.Additionally, the example code has been released to the public domain (see theseparate license for more information).

Table of Contents

• Using libgit2
• Quick Start
• Getting Help
• What It Can Do
• Optional dependencies
• Initialization
• Threading
• Conventions
• Building libgit2 - Using CMake
  • Building
  • Installation
  • Advanced Usage
  • Compiler and linker options
  • MacOS X
  • Android
  • MinGW
• Language Bindings
• How Can I Contribute?
• License

Using libgit2

Most of these instructions assume that you're writing an applicationin C and want to use libgit2 directly. If you're not using C,and you're writing in a different language or platform like .NET,Node.js, or Ruby, then there is probably a"language binding" that you can use to take careof the messy tasks of calling into native code.

But if you do want to use libgit2 directly - because you're buildingan application in C - then you may be able use an existing binary.There are packages for thevcpkg andconanpackage managers. And libgit2 is available inHomebrew and most Linuxdistributions.

However, these versions may be outdated and we recommend using thelatest version if possible. Thankfully libgit2 is not hard to compile.

Quick Start

Prerequisites for building libgit2:

1. CMake, and is recommended to be installed intoyour PATH.
2. Python is used by our test framework, andshould be installed into your PATH.
3. C compiler: libgit2 is C90 and should compile on most compilers.
   • Windows: Visual Studio is recommended
   • Mac: Xcode is recommended
   • Unix: gcc or clang is recommended.

Build

1. Create a build directory beneath the libgit2 source directory, and changeinto it: mkdir build && cd build
2. Create the cmake build environment: cmake ..
3. Build libgit2: cmake --build .

Trouble with these steps? Read our troubleshooting guide.More detailed build guidance is available below.

Getting Help

Chat with us

• via IRC: join #libgit2 onlibera.
• via Slack: visit slack.libgit2.org to sign up,then join us in #libgit2

Getting Help

If you have questions about the library, please be sure to check out theAPI documentation. If you still havequestions, reach out to us on Slack or post a question onStackOverflow (with the libgit2 tag).

Reporting Bugs

Please open a GitHub Issue andinclude as much information as possible. If possible, provide sample codethat illustrates the problem you're seeing. If you're seeing a bug onlyon a specific repository, please provide a link to it if possible.

We ask that you not open a GitHub Issue for help, only for bug reports.

Reporting Security Issues

Please have a look at SECURITY.md.

What It Can Do

libgit2 provides you with the ability to manage Git repositories in theprogramming language of your choice. It's used in production to power manyapplications including GitHub.com, Plastic SCM and Azure DevOps.

It does not aim to replace the git tool or its user-facing commands. Some APIsresemble the plumbing commands as those align closely with the concepts of theGit system, but most commands a user would type are out of scope for thislibrary to implement directly.

The library provides:

• SHA conversions, formatting and shortening
• abstracted ODB backend system
• commit, tag, tree and blob parsing, editing, and write-back
• tree traversal
• revision walking
• index file (staging area) manipulation
• reference management (including packed references)
• config file management
• high level repository management
• thread safety and reentrancy
• descriptive and detailed error messages
• ...and more (over 175 different API calls)

As libgit2 is purely a consumer of the Git system, we have toadjust to changes made upstream. This has two major consequences:

• Some changes may require us to change provided interfaces. While we try toimplement functions in a generic way so that no future changes are required,we cannot promise a completely stable API.
• As we have to keep up with changes in behavior made upstream, we may lagbehind in some areas. We usually to document these incompatibilities in ourissue tracker with the label "git change".

Optional dependencies

While the library provides git functionality without the need fordependencies, it can make use of a few libraries to add to it:

• pthreads (non-Windows) to enable threadsafe access as well as multi-threaded pack generation
• OpenSSL (non-Windows) to talk over HTTPS and provide the SHA-1 functions
• LibSSH2 to enable the SSH transport
• iconv (OSX) to handle the HFS+ path encoding peculiarities

Initialization

The library needs to keep track of some global state. Call

git_libgit2_init();

before calling any other libgit2 functions. You can call this function many times. A matching number of calls to

git_libgit2_shutdown();

will free the resources. Note that if you have worker threads, you shouldcall git_libgit2_shutdown after those threads have exited. If yourequire assistance coordinating this, simply have the worker threads callgit_libgit2_init at startup and git_libgit2_shutdown at shutdown.

Threading

See threading for information

Conventions

See conventions for an overview of the externaland internal API/coding conventions we use.

Building libgit2 - Using CMake

Building

libgit2 builds cleanly on most platforms without any external dependencies.Under Unix-like systems, like Linux, *BSD and Mac OS X, libgit2 expects pthreads to be available;they should be installed by default on all systems. Under Windows, libgit2 uses the native Windows APIfor threading.

The libgit2 library is built using CMake (version 2.8 or newer) on all platforms.

On most systems you can build the library using the following commands

$ mkdir build && cd build$ cmake ..$ cmake --build .

Alternatively you can point the CMake GUI tool to the CMakeLists.txt file and generate platform specific build project or IDE workspace.

If you're not familiar with CMake, a more detailed explanation may be helpful.

Running Tests

Once built, you can run the tests from the build directory with the command

$ ctest -V

Alternatively you can run the test suite directly using,

$ ./libgit2_tests

Invoking the test suite directly is useful because it allows you to executeindividual tests, or groups of tests using the -s flag. For example, torun the index tests:

$ ./libgit2_tests -sindex

To run a single test named index::racy::diff, which corresponds to the testfunction test_index_racy__diff:

$ ./libgit2_tests -sindex::racy::diff

The test suite will print a . for every passing test, and an F for anyfailing test. An S indicates that a test was skipped because it is notapplicable to your platform or is particularly expensive.

Note: There should be no failing tests when you build an unmodifiedsource tree from a release,or from the main branch.Please contact us or open an issueif you see test failures.

Installation

To install the library you can specify the install prefix by setting:

$ cmake .. -DCMAKE_INSTALL_PREFIX=/install/prefix$ cmake --build . --target install

Advanced Usage

For more advanced use or questions about CMake please read https://cmake.org/Wiki/CMake_FAQ.

The following CMake variables are declared:

• CMAKE_INSTALL_BINDIR: Where to install binaries to.
• CMAKE_INSTALL_LIBDIR: Where to install libraries to.
• CMAKE_INSTALL_INCLUDEDIR: Where to install headers to.
• BUILD_SHARED_LIBS: Build libgit2 as a Shared Library (defaults to ON)
• BUILD_TESTS: Build the unit and integration test suites (defaults to ON)
• USE_THREADS: Build libgit2 with threading support (defaults to ON)

To list all build options and their current value, you can do thefollowing:

# Create and set up a build directory$ mkdir build$ cmake ..# List all build options and their values$ cmake -L

Compiler and linker options

CMake lets you specify a few variables to control the behavior of thecompiler and linker. These flags are rarely used but can be useful for64-bit to 32-bit cross-compilation.

• CMAKE_C_FLAGS: Set your own compiler flags
• CMAKE_FIND_ROOT_PATH: Override the search path for libraries
• ZLIB_LIBRARY, OPENSSL_SSL_LIBRARY AND OPENSSL_CRYPTO_LIBRARY:Tell CMake where to find those specific libraries
• LINK_WITH_STATIC_LIBRARIES: Link only with static versions ofsystem libraries

MacOS X

If you want to build a universal binary for Mac OS X, CMake sets itall up for you if you use -DCMAKE_OSX_ARCHITECTURES="i386;x86_64"when configuring.

Android

Extract toolchain from NDK using, make-standalone-toolchain.sh script.Optionally, crosscompile and install OpenSSL inside of it. Then create CMaketoolchain file that configures paths to your crosscompiler (substitute {PATH}with full path to the toolchain):

SET(CMAKE_SYSTEM_NAME Linux)SET(CMAKE_SYSTEM_VERSION Android)SET(CMAKE_C_COMPILER   {PATH}/bin/arm-linux-androideabi-gcc)SET(CMAKE_CXX_COMPILER {PATH}/bin/arm-linux-androideabi-g++)SET(CMAKE_FIND_ROOT_PATH {PATH}/sysroot/)SET(CMAKE_FIND_ROOT_PATH_MODE_PROGRAM NEVER)SET(CMAKE_FIND_ROOT_PATH_MODE_LIBRARY ONLY)SET(CMAKE_FIND_ROOT_PATH_MODE_INCLUDE ONLY)

Add -DCMAKE_TOOLCHAIN_FILE={pathToToolchainFile} to cmake commandwhen configuring.

MinGW

If you want to build the library in MinGW environment with SSH support enabled,you may need to pass -DCMAKE_LIBRARY_PATH="${MINGW_PREFIX}/${MINGW_CHOST}/lib/" flagto CMake when configuring. This is because CMake cannot find the Win32 libraries inMinGW folders by default and you might see an error message stating that CMakecould not resolve ws2_32 library during configuration.

Another option would be to install msys2-w32api-runtime package before configuring.This package installs the Win32 libraries into /usr/lib folder which is by defaultrecognized as the library path by CMake. Please note though that this package is meantfor MSYS subsystem which is different from MinGW.

Language Bindings

Here are the bindings to libgit2 that are currently available:

• C++
  • libqgit2, Qt bindings https://projects.kde.org/projects/playground/libs/libqgit2/repository/
• Chicken Scheme
  • chicken-git https://wiki.call-cc.org/egg/git
• D
  • dlibgit https://github.com/s-ludwig/dlibgit
• Delphi
  • GitForDelphi https://github.com/libgit2/GitForDelphi
  • libgit2-delphi https://github.com/todaysoftware/libgit2-delphi
• Erlang
  • Geef https://github.com/carlosmn/geef
• Go
  • git2go https://github.com/libgit2/git2go
• GObject
  • libgit2-glib https://wiki.gnome.org/Projects/Libgit2-glib
• Guile
  • Guile-Git https://gitlab.com/guile-git/guile-git
• Haskell
  • hgit2 https://github.com/jwiegley/gitlib
• Java
  • Jagged https://github.com/ethomson/jagged
  • Git24j https://github.com/git24j/git24j
• Javascript / WebAssembly ( browser and nodejs )
  • WASM-git https://github.com/petersalomonsen/wasm-git
• Julia
  • LibGit2.jl https://github.com/JuliaLang/julia/tree/master/stdlib/LibGit2
• Lua
  • luagit2 https://github.com/libgit2/luagit2
• .NET
  • libgit2sharp https://github.com/libgit2/libgit2sharp
• Node.js
  • nodegit https://github.com/nodegit/nodegit
• Objective-C
  • objective-git https://github.com/libgit2/objective-git
• OCaml
  • ocaml-libgit2 https://github.com/fxfactorial/ocaml-libgit2
• Parrot Virtual Machine
  • parrot-libgit2 https://github.com/letolabs/parrot-libgit2
• Perl
  • Git-Raw https://github.com/jacquesg/p5-Git-Raw
• PHP
  • php-git https://github.com/libgit2/php-git
• Python
  • pygit2 https://github.com/libgit2/pygit2
• R
  • gert https://docs.ropensci.org/gert
  • git2r https://github.com/ropensci/git2r
• Ruby
  • Rugged https://github.com/libgit2/rugged
• Rust
  • git2-rs https://github.com/rust-lang/git2-rs
• Swift
  • SwiftGit2 https://github.com/SwiftGit2/SwiftGit2
• Vala
  • libgit2.vapi https://github.com/apmasell/vapis/blob/master/libgit2.vapi

If you start another language binding to libgit2, please let us know sowe can add it to the list.

How Can I Contribute?

We welcome new contributors! We have a number of issues marked as"up for grabs"and"easy fix"that are good places to jump in and get started. There's much more detailedinformation in our list of outstanding projects.

Please be sure to check the contribution guidelines tounderstand our workflow, and the libgit2 coding conventions.

License

libgit2 is under GPL2 with linking exception. This means you can link toand use the library from any program, proprietary or open source; paid orgratis. However, if you modify libgit2 itself, you must distribute thesource to your modified version of libgit2.

See the COPYING file for the full license text.