thodg/libgit2

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  • Show log

    Commit

  • Hash : b0d7f329
    Author : Carlos Martín Nieto
    Date : 2015-05-13T10:23:19 

    odb: reverse the default backend priorities

We currently first look in the loose object dir and then in the packs
for objects. When performing operations on recent history this has a
higher likelihood of hitting, but when we deal with operations which
look further back into the past, we start spending a large amount of
time getting ENOTENT from `access`.

Reversing the priorities means that long-running operations can get to
their objects faster, as we can look at the index data we have in memory
(or rather mapped) to figure out whether we have an object, which is
faster than going out to the filesystem.

The packed backend already implements an optimistic read algorithm by
first looking at the packs we know about and only going out to disk to
referesh if the object is not found which means that in the case where
we do have the object (which will be in the majority for anything that
traverses the graph) we can avoid going to to disk entirely to determine
whether an object exists.

Operations which look at recent history may take a slight impact, but
these would be operations which look a lot less at object and thus take
less time regardless.

  • README.md

  • libgit2 - the Git linkable library

    Travis Build Status AppVeyor Build Status Coverity Scan Build Status

    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).

    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 for information

    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 2.6 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 http://www.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](https://libgit2.github.com/docs/guides/build-and-link) for more detailed instructions. Android ------- Extract toolchain from NDK using,make-standalone-toolchain.shscript. 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/AndrejMitrovic/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://live.gnome.org/Libgit2-glib> * Haskell * hgit2 <https://github.com/fpco/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/tbranyen/nodegit> * Objective-C * objective-git <https://github.com/libgit2/objective-git> * OCaml * libgit2-ocaml <https://github.com/burdges/libgit2-ocaml> * 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? ================================== Check the [contribution guidelines](CONTRIBUTING.md) to understand our workflow, the libgit2 [coding conventions](CONVENTIONS.md), and out list of [good starting projects](PROJECTS.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, you cannot modify libgit2 and distribute it without supplying the source. See the COPYING file for the full license text.

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