README.md

   1 libgit2 - the Git linkable library
   2 ==================================
   3
   4 | Build Status | |
   5 | ------------ | - |
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  10
  11 `libgit2` is a portable, pure C implementation of the Git core methods
  12 provided as a linkable library with a solid API, allowing to build Git
  13 functionality into your application.  Language bindings like
  14 [Rugged](https://github.com/libgit2/rugged) (Ruby),
  15 [LibGit2Sharp](https://github.com/libgit2/libgit2sharp) (.NET),
  16 [pygit2](http://www.pygit2.org/) (Python) and
  17 [NodeGit](http://nodegit.org) (Node) allow you to build Git tooling
  18 in your favorite language.
  19
  20 `libgit2` is used to power Git GUI clients like
  21 [GitKraken](https://gitkraken.com/) and [gmaster](https://gmaster.io/)
  22 and on Git hosting providers like [GitHub](https://github.com/),
  23 [GitLab](https://gitlab.com/) and
  24 [Azure DevOps](https://azure.com/devops).
  25 We perform the merge every time you click "merge pull request".
  26
  27 `libgit2` is licensed under a **very permissive license** (GPLv2 with a special
  28 Linking Exception).  This basically means that you can link it (unmodified)
  29 with any kind of software without having to release its source code.
  30 Additionally, the example code has been released to the public domain (see the
  31 [separate license](examples/COPYING) for more information).
  32
  33 Table of Contents
  34 =================
  35
  36 * [Using libgit2](#using-libgit2)
  37 * [Quick Start](#quick-start)
  38 * [Getting Help](#getting-help)
  39 * [What It Can Do](#what-it-can-do)
  40 * [Optional dependencies](#optional-dependencies)
  41 * [Initialization](#initialization)
  42 * [Threading](#threading)
  43 * [Conventions](#conventions)
  44 * [Building libgit2 - Using CMake](#building-libgit2---using-cmake)
  45     * [Building](#building)
  46     * [Installation](#installation)
  47     * [Advanced Usage](#advanced-usage)
  48     * [Compiler and linker options](#compiler-and-linker-options)
  49     * [MacOS X](#macos-x)
  50     * [Android](#android)
  51     * [MinGW](#mingw)
  52 * [Language Bindings](#language-bindings)
  53 * [How Can I Contribute?](#how-can-i-contribute)
  54 * [License](#license)
  55
  56 Using libgit2
  57 =============
  58
  59 Most of these instructions assume that you're writing an application
  60 in C and want to use libgit2 directly.  If you're _not_ using C,
  61 and you're writing in a different language or platform like .NET,
  62 Node.js, or Ruby, then there is probably a
  63 "[language binding](#language-bindings)" that you can use to take care
  64 of the messy tasks of calling into native code.
  65
  66 But if you _do_ want to use libgit2 directly - because you're building
  67 an application in C - then you may be able use an existing binary.
  68 There are packages for the
  69 [vcpkg](https://github.com/Microsoft/vcpkg) and
  70 [conan](https://conan.io/center/libgit2)
  71 package managers.  And libgit2 is available in
  72 [Homebrew](https://formulae.brew.sh/formula/libgit2) and most Linux
  73 distributions.
  74
  75 However, these versions _may_ be outdated and we recommend using the
  76 latest version if possible.  Thankfully libgit2 is not hard to compile.
  77
  78 Quick Start
  79 ===========
  80
  81 **Prerequisites** for building libgit2:
  82
  83 1. [CMake](https://cmake.org/), and is recommended to be installed into
  84    your `PATH`.
  85 2. [Python](https://www.python.org) is used by our test framework, and
  86    should be installed into your `PATH`.
  87 3. C compiler: libgit2 is C90 and should compile on most compilers.
  88    * Windows: Visual Studio is recommended
  89    * Mac: Xcode is recommended
  90    * Unix: gcc or clang is recommended.
  91
  92 **Build**
  93
  94 1. Create a build directory beneath the libgit2 source directory, and change
  95    into it: `mkdir build && cd build`
  96 2. Create the cmake build environment: `cmake ..`
  97 3. Build libgit2: `cmake --build .`
  98
  99 Trouble with these steps?  Read our [troubleshooting guide](docs/troubleshooting.md).
 100 More detailed build guidance is available below.
 101
 102 Getting Help
 103 ============
 104
 105 **Chat with us**
 106
 107 - via IRC: join [#libgit2](https://web.libera.chat/#libgit2) on
 108   [libera](https://libera.chat).
 109 - via Slack: visit [slack.libgit2.org](http://slack.libgit2.org/) to sign up,
 110   then join us in `#libgit2`
 111
 112 **Getting Help**
 113
 114 If you have questions about the library, please be sure to check out the
 115 [API documentation](http://libgit2.github.com/libgit2/).  If you still have
 116 questions, reach out to us on Slack or post a question on
 117 [StackOverflow](http://stackoverflow.com/questions/tagged/libgit2) (with the `libgit2` tag).
 118
 119 **Reporting Bugs**
 120
 121 Please open a [GitHub Issue](https://github.com/libgit2/libgit2/issues) and
 122 include as much information as possible.  If possible, provide sample code
 123 that illustrates the problem you're seeing.  If you're seeing a bug only
 124 on a specific repository, please provide a link to it if possible.
 125
 126 We ask that you not open a GitHub Issue for help, only for bug reports.
 127
 128 **Reporting Security Issues**
 129
 130 Please have a look at SECURITY.md.
 131
 132 What It Can Do
 133 ==============
 134
 135 libgit2 provides you with the ability to manage Git repositories in the
 136 programming language of your choice.  It's used in production to power many
 137 applications including GitHub.com, Plastic SCM and Azure DevOps.
 138
 139 It does not aim to replace the git tool or its user-facing commands. Some APIs
 140 resemble the plumbing commands as those align closely with the concepts of the
 141 Git system, but most commands a user would type are out of scope for this
 142 library to implement directly.
 143
 144 The library provides:
 145
 146 * SHA conversions, formatting and shortening
 147 * abstracted ODB backend system
 148 * commit, tag, tree and blob parsing, editing, and write-back
 149 * tree traversal
 150 * revision walking
 151 * index file (staging area) manipulation
 152 * reference management (including packed references)
 153 * config file management
 154 * high level repository management
 155 * thread safety and reentrancy
 156 * descriptive and detailed error messages
 157 * ...and more (over 175 different API calls)
 158
 159 As libgit2 is purely a consumer of the Git system, we have to
 160 adjust to changes made upstream. This has two major consequences:
 161
 162 * Some changes may require us to change provided interfaces. While we try to
 163   implement functions in a generic way so that no future changes are required,
 164   we cannot promise a completely stable API.
 165 * As we have to keep up with changes in behavior made upstream, we may lag
 166   behind in some areas. We usually to document these incompatibilities in our
 167   issue tracker with the label "git change".
 168
 169 Optional dependencies
 170 =====================
 171
 172 While the library provides git functionality without the need for
 173 dependencies, it can make use of a few libraries to add to it:
 174
 175 - pthreads (non-Windows) to enable threadsafe access as well as multi-threaded pack generation
 176 - OpenSSL (non-Windows) to talk over HTTPS and provide the SHA-1 functions
 177 - LibSSH2 to enable the SSH transport
 178 - iconv (OSX) to handle the HFS+ path encoding peculiarities
 179
 180 Initialization
 181 ===============
 182
 183 The library needs to keep track of some global state. Call
 184
 185     git_libgit2_init();
 186
 187 before calling any other libgit2 functions. You can call this function many times. A matching number of calls to
 188
 189     git_libgit2_shutdown();
 190
 191 will free the resources.  Note that if you have worker threads, you should
 192 call `git_libgit2_shutdown` *after* those threads have exited.  If you
 193 require assistance coordinating this, simply have the worker threads call
 194 `git_libgit2_init` at startup and `git_libgit2_shutdown` at shutdown.
 195
 196 Threading
 197 =========
 198
 199 See [threading](docs/threading.md) for information
 200
 201 Conventions
 202 ===========
 203
 204 See [conventions](docs/conventions.md) for an overview of the external
 205 and internal API/coding conventions we use.
 206
 207 Building libgit2 - Using CMake
 208 ==============================
 209
 210 Building
 211 --------
 212
 213 `libgit2` builds cleanly on most platforms without any external dependencies.
 214 Under Unix-like systems, like Linux, \*BSD and Mac OS X, libgit2 expects `pthreads` to be available;
 215 they should be installed by default on all systems. Under Windows, libgit2 uses the native Windows API
 216 for threading.
 217
 218 The `libgit2` library is built using [CMake](<https://cmake.org/>) (version 2.8 or newer) on all platforms.
 219
 220 On most systems you can build the library using the following commands
 221
 222         $ mkdir build && cd build
 223         $ cmake ..
 224         $ cmake --build .
 225
 226 Alternatively you can point the CMake GUI tool to the CMakeLists.txt file and generate platform specific build project or IDE workspace.
 227
 228 If you're not familiar with CMake, [a more detailed explanation](https://preshing.com/20170511/how-to-build-a-cmake-based-project/) may be helpful.
 229
 230 Running Tests
 231 -------------
 232
 233 Once built, you can run the tests from the `build` directory with the command
 234
 235         $ ctest -V
 236
 237 Alternatively you can run the test suite directly using,
 238
 239         $ ./libgit2_clar
 240
 241 Invoking the test suite directly is useful because it allows you to execute
 242 individual tests, or groups of tests using the `-s` flag.  For example, to
 243 run the index tests:
 244
 245     $ ./libgit2_clar -sindex
 246
 247 To run a single test named `index::racy::diff`, which corresponds to the test
 248 function [`test_index_racy__diff`](https://github.com/libgit2/libgit2/blob/main/tests/index/racy.c#L23):
 249
 250     $ ./libgit2_clar -sindex::racy::diff
 251
 252 The test suite will print a `.` for every passing test, and an `F` for any
 253 failing test.  An `S` indicates that a test was skipped because it is not
 254 applicable to your platform or is particularly expensive.
 255
 256 **Note:** There should be _no_ failing tests when you build an unmodified
 257 source tree from a [release](https://github.com/libgit2/libgit2/releases),
 258 or from the [main branch](https://github.com/libgit2/libgit2/tree/main).
 259 Please contact us or [open an issue](https://github.com/libgit2/libgit2/issues)
 260 if you see test failures.
 261
 262 Installation
 263 ------------
 264
 265 To install the library you can specify the install prefix by setting:
 266
 267         $ cmake .. -DCMAKE_INSTALL_PREFIX=/install/prefix
 268         $ cmake --build . --target install
 269
 270 Advanced Usage
 271 --------------
 272
 273 For more advanced use or questions about CMake please read <https://cmake.org/Wiki/CMake_FAQ>.
 274
 275 The following CMake variables are declared:
 276
 277 - `CMAKE_INSTALL_BINDIR`: Where to install binaries to.
 278 - `CMAKE_INSTALL_LIBDIR`: Where to install libraries to.
 279 - `CMAKE_INSTALL_INCLUDEDIR`: Where to install headers to.
 280 - `BUILD_SHARED_LIBS`: Build libgit2 as a Shared Library (defaults to ON)
 281 - `BUILD_CLAR`: Build [Clar](https://github.com/vmg/clar)-based test suite (defaults to ON)
 282 - `THREADSAFE`: Build libgit2 with threading support (defaults to ON)
 283
 284 To list all build options and their current value, you can do the
 285 following:
 286
 287         # Create and set up a build directory
 288         $ mkdir build
 289         $ cmake ..
 290         # List all build options and their values
 291         $ cmake -L
 292
 293 Compiler and linker options
 294 ---------------------------
 295
 296 CMake lets you specify a few variables to control the behavior of the
 297 compiler and linker. These flags are rarely used but can be useful for
 298 64-bit to 32-bit cross-compilation.
 299
 300 - `CMAKE_C_FLAGS`: Set your own compiler flags
 301 - `CMAKE_FIND_ROOT_PATH`: Override the search path for libraries
 302 - `ZLIB_LIBRARY`, `OPENSSL_SSL_LIBRARY` AND `OPENSSL_CRYPTO_LIBRARY`:
 303 Tell CMake where to find those specific libraries
 304
 305 MacOS X
 306 -------
 307
 308 If you want to build a universal binary for Mac OS X, CMake sets it
 309 all up for you if you use `-DCMAKE_OSX_ARCHITECTURES="i386;x86_64"`
 310 when configuring.
 311
 312 Android
 313 -------
 314
 315 Extract toolchain from NDK using, `make-standalone-toolchain.sh` script.
 316 Optionally, crosscompile and install OpenSSL inside of it. Then create CMake
 317 toolchain file that configures paths to your crosscompiler (substitute `{PATH}`
 318 with full path to the toolchain):
 319
 320         SET(CMAKE_SYSTEM_NAME Linux)
 321         SET(CMAKE_SYSTEM_VERSION Android)
 322
 323         SET(CMAKE_C_COMPILER   {PATH}/bin/arm-linux-androideabi-gcc)
 324         SET(CMAKE_CXX_COMPILER {PATH}/bin/arm-linux-androideabi-g++)
 325         SET(CMAKE_FIND_ROOT_PATH {PATH}/sysroot/)
 326
 327         SET(CMAKE_FIND_ROOT_PATH_MODE_PROGRAM NEVER)
 328         SET(CMAKE_FIND_ROOT_PATH_MODE_LIBRARY ONLY)
 329         SET(CMAKE_FIND_ROOT_PATH_MODE_INCLUDE ONLY)
 330
 331 Add `-DCMAKE_TOOLCHAIN_FILE={pathToToolchainFile}` to cmake command
 332 when configuring.
 333
 334 MinGW
 335 -----
 336
 337 If you want to build the library in MinGW environment with SSH support enabled,
 338 you may need to pass `-DCMAKE_LIBRARY_PATH="${MINGW_PREFIX}/${MINGW_CHOST}/lib/"` flag
 339 to CMake when configuring. This is because CMake cannot find the Win32 libraries in
 340 MinGW folders by default and you might see an error message stating that CMake
 341 could not resolve `ws2_32` library during configuration.
 342
 343 Another option would be to install `msys2-w32api-runtime` package before configuring.
 344 This package installs the Win32 libraries into `/usr/lib` folder which is by default
 345 recognized as the library path by CMake. Please note though that this package is meant
 346 for MSYS subsystem which is different from MinGW.
 347
 348 Language Bindings
 349 ==================================
 350
 351 Here are the bindings to libgit2 that are currently available:
 352
 353 * C++
 354     * libqgit2, Qt bindings <https://projects.kde.org/projects/playground/libs/libqgit2/repository/>
 355 * Chicken Scheme
 356     * chicken-git <https://wiki.call-cc.org/egg/git>
 357 * D
 358     * dlibgit <https://github.com/s-ludwig/dlibgit>
 359 * Delphi
 360     * GitForDelphi <https://github.com/libgit2/GitForDelphi>
 361     * libgit2-delphi <https://github.com/todaysoftware/libgit2-delphi>
 362 * Erlang
 363     * Geef <https://github.com/carlosmn/geef>
 364 * Go
 365     * git2go <https://github.com/libgit2/git2go>
 366 * GObject
 367     * libgit2-glib <https://wiki.gnome.org/Projects/Libgit2-glib>
 368 * Guile
 369         * Guile-Git <https://gitlab.com/guile-git/guile-git>
 370 * Haskell
 371     * hgit2 <https://github.com/jwiegley/gitlib>
 372 * Java
 373     * Jagged <https://github.com/ethomson/jagged>
 374     * Git24j <https://github.com/git24j/git24j>
 375 * Javascript / WebAssembly ( browser and nodejs )
 376     * WASM-git <https://github.com/petersalomonsen/wasm-git>
 377 * Julia
 378     * LibGit2.jl <https://github.com/JuliaLang/julia/tree/master/stdlib/LibGit2>
 379 * Lua
 380     * luagit2 <https://github.com/libgit2/luagit2>
 381 * .NET
 382     * libgit2sharp <https://github.com/libgit2/libgit2sharp>
 383 * Node.js
 384     * nodegit <https://github.com/nodegit/nodegit>
 385 * Objective-C
 386     * objective-git <https://github.com/libgit2/objective-git>
 387 * OCaml
 388     * ocaml-libgit2 <https://github.com/fxfactorial/ocaml-libgit2>
 389 * Parrot Virtual Machine
 390     * parrot-libgit2 <https://github.com/letolabs/parrot-libgit2>
 391 * Perl
 392     * Git-Raw <https://github.com/jacquesg/p5-Git-Raw>
 393 * PHP
 394     * php-git <https://github.com/libgit2/php-git>
 395 * PowerShell
 396     * PSGit <https://github.com/PoshCode/PSGit>
 397 * Python
 398     * pygit2 <https://github.com/libgit2/pygit2>
 399 * R
 400     * gert <https://docs.ropensci.org/gert>
 401     * git2r <https://github.com/ropensci/git2r>
 402 * Ruby
 403     * Rugged <https://github.com/libgit2/rugged>
 404 * Rust
 405     * git2-rs <https://github.com/rust-lang/git2-rs>
 406 * Swift
 407     * SwiftGit2 <https://github.com/SwiftGit2/SwiftGit2>
 408 * Vala
 409     * libgit2.vapi <https://github.com/apmasell/vapis/blob/master/libgit2.vapi>
 410
 411 If you start another language binding to libgit2, please let us know so
 412 we can add it to the list.
 413
 414 How Can I Contribute?
 415 ==================================
 416
 417 We welcome new contributors!  We have a number of issues marked as
 418 ["up for grabs"](https://github.com/libgit2/libgit2/issues?q=is%3Aissue+is%3Aopen+label%3A%22up+for+grabs%22)
 419 and
 420 ["easy fix"](https://github.com/libgit2/libgit2/issues?utf8=✓&q=is%3Aissue+is%3Aopen+label%3A%22easy+fix%22)
 421 that are good places to jump in and get started.  There's much more detailed
 422 information in our list of [outstanding projects](docs/projects.md).
 423
 424 Please be sure to check the [contribution guidelines](docs/contributing.md) to
 425 understand our workflow, and the libgit2 [coding conventions](docs/conventions.md).
 426
 427 License
 428 ==================================
 429
 430 `libgit2` is under GPL2 **with linking exception**. This means you can link to
 431 and use the library from any program, proprietary or open source; paid or
 432 gratis.  However, if you modify libgit2 itself, you must distribute the
 433 source to your modified version of libgit2.
 434
 435 See the [COPYING file](COPYING) for the full license text.