README.md - third_party/libgit2 - Git at Google

 libgit2 - the Git linkable library
 ==================================

 [![Travis Build Status](https://secure.travis-ci.org/libgit2/libgit2.svg?branch=master)](http://travis-ci.org/libgit2/libgit2)
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 [![Coverity Scan Build Status](https://scan.coverity.com/projects/639/badge.svg)](https://scan.coverity.com/projects/639)

 `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` is already very usable and is being used in production for many
 applications including the GitHub.com site, in Plastic SCM and also powering
 Microsoft's Visual Studio tools for Git.  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)

 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.

 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/>
 * 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
     * node-gitteh <https://github.com/libgit2/node-gitteh>
     * 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
     * GitPowerShell <https://github.com/ethomson/gitpowershell>
 * 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
     * Gift <https://github.com/modocache/Gift>
 * 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.
	libgit2 - the Git linkable library
	==================================

	[![Travis Build Status](https://secure.travis-ci.org/libgit2/libgit2.svg?branch=master)](http://travis-ci.org/libgit2/libgit2)
	[![AppVeyor Build Status](https://ci.appveyor.com/api/projects/status/xvof5b4t5480a2q3/branch/master?svg=true)](https://ci.appveyor.com/project/libgit2/libgit2/branch/master)
	[![Coverity Scan Build Status](https://scan.coverity.com/projects/639/badge.svg)](https://scan.coverity.com/projects/639)

	`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` is already very usable and is being used in production for many
	applications including the GitHub.com site, in Plastic SCM and also powering
	Microsoft's Visual Studio tools for Git. 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)

	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.

	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/>
	* 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
	* node-gitteh <https://github.com/libgit2/node-gitteh>
	* 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
	* GitPowerShell <https://github.com/ethomson/gitpowershell>
	* 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
	* Gift <https://github.com/modocache/Gift>
	* 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.