libgit2 - the Git linkable library

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.

Why Do We Need It

In the current Git project, though a libgit.a file is produced it is not re-entrant (it will call <code>die()</code> on basically any error) and it has no stable or well-designed public API. As there is no good way to link to this effectively, a new library was needed that fulfilled these requirements. Thus libgit2.

Though it would be nice to use the same library that Git itself uses, Git actually has a pretty simple storage format and just having native access to that is pretty useful. Eventually we would like to have most of the functionality of the core Git tools or even get the library integrated into Git itself, but in the meantime having a cleanly designed and maintained linkable Git library with a public API will likely be helpful to lots of people.

What It Can Do

libgit2 is already very usable.

• raw <-> hex SHA conversions
• raw object reading (loose and packed)
• raw object writing (loose)
• revlist walker
• commit, tag and tree object parsing and write-back
• tree traversal
• basic index file (staging area) operations

Building libgit2 - Using CMake

When building using CMake the following dependencies are required:

• CMake 2.6+ http://www.cmake.org

Required dependency:

• zlib 1.2+ http://www.zlib.net/

Optional dependency:

• LibSSL http://www.openssl.org/

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.

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 http://www.cmake.org/Wiki/CMake_FAQ.

Building libgit2 - Unix systems

In Unix-like systems, like Linux, xBSD and Mac OS X, libgit2 has the following dependencies:

• Python 2.5-3.1 http://www.python.org

Used to run the build system; no extra libraries required. Should probably ship installed with your OS.

• zlib 1.2+ http://www.zlib.net/

• LibSSL http://www.openssl.org/

Only needed if you want to re-use OpenSSL’s SHA1 routines; libgit2 compiles its own routines by default.

To build it, first configure the build system by running:

$ ./waf configure

Then build the library, either in its shared (libgit2.so) or static form (libgit2.a)

$ ./waf build-static
$ ./waf build-shared

You can then test the library with:

$ ./waf test

And finally you can install it with (you may need to sudo):

$ ./waf install

Building libgit2 - Windows MSVC++

When building under Windows using the MSVC compiler, libgit2 has the following dependencies:

• Python 2.5-3.1 http://www.python.org

Used to run the build system; no extra libraries required.

• zlib 1.2+ (Windows API Version) http://www.zlib.net/

Make sure you compile the ZLib library using the MSVC solution that ships in its source distribution. Alternatively, you may download precompiled binaries from: http://www.winimage.com/zLibDll/

• LibSSL http://www.openssl.org/

Only needed if you want to re-use OpenSSL’s SHA1 routines; libgit2 compiles its own routines by default.

To build it, first configure the build system by running:

$ ./waf configure

Then build the library, either in its shared (libgit2.dll) or static form (libgit2.lib)

$ ./waf build-static
$ ./waf build-shared

You can then test the library with:

$ ./waf test

Lastly, you can manually install the generated .lib and .dll files, depending on your preferences.

Building libgit2 - Windows MinGW

When building under Windows using the GCC compiler that ships with MinGW, libgit2 has the following dependencies:

• Python 2.5-3.1 http://www.python.org

Used to run the build system; no extra libraries required.

• zlib 1.2+ http://www.zlib.net/

• pthreads-w32 http://sourceware.org/pthreads-win32/

Or an equivalent pthreads implementation for non-POSIX systems

• LibSSL http://www.openssl.org/

Only needed if you want to re-use OpenSSL’s SHA1 routines; libgit2 compiles its own routines by default.

To build it, first configure the build system and force GCC as the compiler, instead of the default MSVC:

$ ./waf configure --check-c-compiler=gcc

Then build the library, either in its shared (libgit2.so) or static form (libgit2.a)

$ ./waf build-static
$ ./waf build-shared

You can then test the library with:

$ ./waf test

And finally you can install it with:

$ ./waf install

Configuration settings

The waf build system for libgit2 accepts the following flags:

--debug
    build the library with debug symbols.
    Defaults to off.

--sha1=[builtin|ppc|openssl]
    use the builtin SHA1 functions, the optimized PPC versions
    or the SHA1 functions from LibCrypto (OpenSSL).
    Defaults to 'builtin'.

--msvc=[7.1|8.0|9.0|10.0]
    Force a specific version of the MSVC compiler, if more than
    one version is installed.

--arch=[ia64|x64|x86|x86_amd64|x86_ia64]
    Force a specific architecture for compilers that support it.

You can run ./waf --help to see a full list of install options and targets.

Language Bindings

So you want to use Git from your favorite programming language. Here are the bindings to libgit2 that are currently available:

Ruby

Rugged is the reference library used to make sure the libgit2 API is sane. This should be mostly up to date.

https://github.com/libgit2/rugged

Python

Pygit2 is a Python binding to libgit2.

https://github.com/libgit2/pygit2

Erlang

Geef is an example of an Erlang NIF binding to libgit2. A bit out of date, but basically works. Best as a proof of concept of what you could do with Erlang and NIFs with libgit2.

https://github.com/schacon/geef

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

How Can I Contribute

Fork libgit2/libgit2 on GitHub, add your improvement, push it to a branch in your fork named for the topic, send a pull request.

You can also file bugs or feature requests under the libgit2 project on GitHub, or join us on the mailing list by sending an email to:

libgit2@librelist.com

License

libgit2 is under GPL2 with linking exemption, which basically means you can link to the library with any program, commercial, open source or other. However, you cannot modify libgit2 and distribute it without supplying the source.

See the COPYING file for the full license text.