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libgit2 - the Git linkable library

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libgit2 is a portable, pure C implementation of the Git core methods provided as a re-entrant linkable library with a solid API, allowing you to write native speed custom Git applications in any language with bindings.

libgit2 is licensed under a very permissive license (GPLv2 with a special Linking 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 the separate license for more information).

Getting Help

Join us on Slack

Visit slack.libgit2.org to sign up, then join us in #libgit2. If you prefer IRC, you can also point your client to our slack channel once you've registered.

Getting Help

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

Reporting Bugs

Please open a GitHub Issue and include as much information as possible. If possible, provide sample code that illustrates the problem you're seeing. If you're seeing a bug only on 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.

What It Can Do

The goal of this library is to allow its users the ability to handle Git data in their applications from their programming language of choice, as is used in production for many applications including the GitHub.com site, in Plastic SCM and also powering Microsoft's Visual Studio tools for Git.

It does not aim to replace the git tool or its user-facing commands. Some APIs resemble the plumbing commands as those align closely with the concepts of the Git system, but most commands a user would type are out of scope for this library 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 to adjust to changes made upstream. This has two major consequences:

  • Some changes may require us to change provided interfaces. While we try to implement 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 lag behind in some areas. We usually to document these incompatibilities in our issue tracker with the label "git change".

Optional dependencies

While the library provides git functionality without the need for dependencies, 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 should call git_libgit2_shutdown after those threads have exited. If you require assistance coordinating this, simply have the worker threads call git_libgit2_init at startup and git_libgit2_shutdown at shutdown.

Threading

See THREADING for information

Conventions

See CONVENTIONS for an overview of the external and internal API/coding conventions we use.

Building libgit2 - Using CMake

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 API for 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.

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

$ make test

Alternatively you can run the test suite directly using,

$ ./libgit2_clar

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

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

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

The following CMake variables are declared:

  • BIN_INSTALL_DIR: Where to install binaries to.
  • LIB_INSTALL_DIR: Where to install libraries to.
  • INCLUDE_INSTALL_DIR: Where to install headers to.
  • BUILD_SHARED_LIBS: Build libgit2 as a Shared Library (defaults to ON)
  • BUILD_CLAR: Build Clar-based test suite (defaults to ON)
  • THREADSAFE: Build libgit2 with threading support (defaults to ON)
  • STDCALL: Build libgit2 as stdcall. Turn off for cdecl (Windows; defaults to ON)

Compiler and linker options

CMake lets you specify a few variables to control the behavior of the compiler and linker. These flags are rarely used but can be useful for 64-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

MacOS X

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

Windows

You need to run the CMake commands from the Visual Studio command prompt, not the regular or Windows SDK one. Select the right generator for your version with the `-G "Visual Studio X" option.

See the website for more detailed instructions.

Android

Extract toolchain from NDK using, make-standalone-toolchain.sh script. Optionally, crosscompile and install OpenSSL inside of it. Then create CMake toolchain 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 command when configuring.

Language Bindings

Here are the bindings to libgit2 that are currently available:

If you start another language binding to libgit2, please let us know so we 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 detailed information in our list of outstanding projects.

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

License

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

See the COPYING file for the full license text.