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](examples/COPYING) for more information).

Getting Help

============

**Join us on Slack**

Visit [slack.libgit2.org](http://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](http://libgit2.github.com/libgit2/).  If you still have

questions, reach out to us on Slack or post a question on 

[StackOverflow](http://stackoverflow.com/questions/tagged/libgit2) (with the `libgit2` tag).

**Reporting Bugs**

Please open a [GitHub Issue](https://github.com/libgit2/libgit2/issues) 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

==============

libgit2 provides you with the ability to manage Git repositories in the

programming language of your choice.  It's used in production to power many

applications including GitHub.com, Plastic SCM and Azure DevOps.

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](THREADING.md) for information

Conventions

===========

See [CONVENTIONS](CONVENTIONS.md) 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](<https://cmake.org/>) (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](https://github.com/vmg/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](http://libgit2.github.com/docs/guides/build-and-link/)

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:

* 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>

* Erlang

    * Geef <https://github.com/carlosmn/geef>

* Go

    * git2go <https://github.com/libgit2/git2go>

* GObject

    * libgit2-glib <https://wiki.gnome.org/Projects/Libgit2-glib>

* Haskell

    * hgit2 <https://github.com/jwiegley/gitlib>

* Java

    * Jagged <https://github.com/ethomson/jagged>

* Julia

    * LibGit2.jl <https://github.com/jakebolewski/LibGit2.jl>

* 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>

* PowerShell

    * PSGit <https://github.com/PoshCode/PSGit>

* Python

    * pygit2 <https://github.com/libgit2/pygit2>

* R

    * git2r <https://github.com/ropensci/git2r>

* Ruby

    * Rugged <https://github.com/libgit2/rugged>

* Rust

    * git2-rs <https://github.com/alexcrichton/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 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"](https://github.com/libgit2/libgit2/issues?q=is%3Aissue+is%3Aopen+label%3A%22up+for+grabs%22)

and

["easy fix"](https://github.com/libgit2/libgit2/issues?utf8=✓&q=is%3Aissue+is%3Aopen+label%3A%22easy+fix%22)

that are good places to jump in and get started.  There's much more detailed

information in our list of [outstanding projects](PROJECTS.md).

Please be sure to check the [contribution guidelines](CONTRIBUTING.md) to

understand our workflow, and the libgit2 [coding conventions](CONVENTIONS.md).

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](COPYING) for the full license text.