Gordon Murray

Gordon Murray

1679133267

Libgit2: The Git Linkable Library

libgit2 - the Git linkable library

libgit2 is a portable, pure C implementation of the Git core methods provided as a linkable library with a solid API, allowing to build Git functionality into your application. Language bindings like Rugged (Ruby), LibGit2Sharp (.NET), pygit2 (Python) and NodeGit (Node) allow you to build Git tooling in your favorite language.

libgit2 is used to power Git GUI clients like GitKraken and gmaster and on Git hosting providers like GitHub, GitLab and Azure DevOps. We perform the merge every time you click "merge pull request".

libgit2 is licensed under a very permissive license (GPLv2 with a special Linking Exception). This means that you can link against the library with any kind of software without making that software fall under the GPL. Changes to libgit2 would still be covered under its GPL license. Additionally, the example code has been released to the public domain (see the separate license for more information).

Using libgit2

Most of these instructions assume that you're writing an application in C and want to use libgit2 directly. If you're not using C, and you're writing in a different language or platform like .NET, Node.js, or Ruby, then there is probably a "language binding" that you can use to take care of the messy tasks of calling into native code.

But if you do want to use libgit2 directly - because you're building an application in C - then you may be able use an existing binary. There are packages for the vcpkg and conan package managers. And libgit2 is available in Homebrew and most Linux distributions.

However, these versions may be outdated and we recommend using the latest version if possible. Thankfully libgit2 is not hard to compile.

Quick Start

Prerequisites for building libgit2:

  1. CMake, and is recommended to be installed into your PATH.
  2. Python is used by our test framework, and should be installed into your PATH.
  3. C compiler: libgit2 is C90 and should compile on most compilers.
    • Windows: Visual Studio is recommended
    • Mac: Xcode is recommended
    • Unix: gcc or clang is recommended.

Build

  1. Create a build directory beneath the libgit2 source directory, and change into it: mkdir build && cd build
  2. Create the cmake build environment: cmake ..
  3. Build libgit2: cmake --build .

Trouble with these steps? Read our troubleshooting guide. More detailed build guidance is available below.

Getting Help

Chat with us

Getting Help

If you have questions about the library, please be sure to check out the API documentation. If you still have questions, reach out to us on Slack or post a question on StackOverflow (with the libgit2 tag).

Reporting Bugs

Please open a GitHub Issue 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.

Reporting Security Issues

Please have a look at SECURITY.md.

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 for information

Conventions

See conventions for an overview of the external and internal API/coding conventions we use.

Building libgit2 - Using CMake

Building

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 2.8 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.

If you're not familiar with CMake, a more detailed explanation may be helpful.

Running Tests

Once built, you can run the tests from the build directory with the command

$ ctest -V

Alternatively you can run the test suite directly using,

$ ./libgit2_tests

Invoking the test suite directly is useful because it allows you to execute individual tests, or groups of tests using the -s flag. For example, to run the index tests:

$ ./libgit2_tests -sindex

To run a single test named index::racy::diff, which corresponds to the test function test_index_racy__diff:

$ ./libgit2_tests -sindex::racy::diff

The test suite will print a . for every passing test, and an F for any failing test. An S indicates that a test was skipped because it is not applicable to your platform or is particularly expensive.

Note: There should be no failing tests when you build an unmodified source tree from a release, or from the main branch. Please contact us or open an issue if you see test failures.

Installation

To install the library you can specify the install prefix by setting:

$ cmake .. -DCMAKE_INSTALL_PREFIX=/install/prefix
$ cmake --build . --target install

Advanced Usage

For more advanced use or questions about CMake please read https://cmake.org/Wiki/CMake_FAQ.

The following CMake variables are declared:

  • CMAKE_INSTALL_BINDIR: Where to install binaries to.
  • CMAKE_INSTALL_LIBDIR: Where to install libraries to.
  • CMAKE_INSTALL_INCLUDEDIR: Where to install headers to.
  • BUILD_SHARED_LIBS: Build libgit2 as a Shared Library (defaults to ON)
  • BUILD_TESTS: Build the unit and integration test suites (defaults to ON)
  • USE_THREADS: Build libgit2 with threading support (defaults to ON)

To list all build options and their current value, you can do the following:

# Create and set up a build directory
$ mkdir build
$ cmake ..
# List all build options and their values
$ cmake -L

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
  • LINK_WITH_STATIC_LIBRARIES: Link only with static versions of system 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.

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.

MinGW

If you want to build the library in MinGW environment with SSH support enabled, you may need to pass -DCMAKE_LIBRARY_PATH="${MINGW_PREFIX}/${MINGW_CHOST}/lib/" flag to CMake when configuring. This is because CMake cannot find the Win32 libraries in MinGW folders by default and you might see an error message stating that CMake could not resolve ws2_32 library during configuration.

Another option would be to install msys2-w32api-runtime package before configuring. This package installs the Win32 libraries into /usr/lib folder which is by default recognized as the library path by CMake. Please note though that this package is meant for MSYS subsystem which is different from MinGW.

Language Bindings

Here are the bindings to libgit2 that are currently available:

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" and "easy fix" that are good places to jump in and get started. There's much more detailed information in our list of outstanding projects.

Please be sure to check the contribution guidelines to understand our workflow, and the libgit2 coding conventions.

Download Details:

Author: libgit2
Source Code: https://github.com/libgit2/libgit2 
License: View license

#c #git #library #versioncontrols #hacktoberfest 

What is GEEK

Buddha Community

Libgit2: The Git Linkable Library
Gordon Murray

Gordon Murray

1679133267

Libgit2: The Git Linkable Library

libgit2 - the Git linkable library

libgit2 is a portable, pure C implementation of the Git core methods provided as a linkable library with a solid API, allowing to build Git functionality into your application. Language bindings like Rugged (Ruby), LibGit2Sharp (.NET), pygit2 (Python) and NodeGit (Node) allow you to build Git tooling in your favorite language.

libgit2 is used to power Git GUI clients like GitKraken and gmaster and on Git hosting providers like GitHub, GitLab and Azure DevOps. We perform the merge every time you click "merge pull request".

libgit2 is licensed under a very permissive license (GPLv2 with a special Linking Exception). This means that you can link against the library with any kind of software without making that software fall under the GPL. Changes to libgit2 would still be covered under its GPL license. Additionally, the example code has been released to the public domain (see the separate license for more information).

Using libgit2

Most of these instructions assume that you're writing an application in C and want to use libgit2 directly. If you're not using C, and you're writing in a different language or platform like .NET, Node.js, or Ruby, then there is probably a "language binding" that you can use to take care of the messy tasks of calling into native code.

But if you do want to use libgit2 directly - because you're building an application in C - then you may be able use an existing binary. There are packages for the vcpkg and conan package managers. And libgit2 is available in Homebrew and most Linux distributions.

However, these versions may be outdated and we recommend using the latest version if possible. Thankfully libgit2 is not hard to compile.

Quick Start

Prerequisites for building libgit2:

  1. CMake, and is recommended to be installed into your PATH.
  2. Python is used by our test framework, and should be installed into your PATH.
  3. C compiler: libgit2 is C90 and should compile on most compilers.
    • Windows: Visual Studio is recommended
    • Mac: Xcode is recommended
    • Unix: gcc or clang is recommended.

Build

  1. Create a build directory beneath the libgit2 source directory, and change into it: mkdir build && cd build
  2. Create the cmake build environment: cmake ..
  3. Build libgit2: cmake --build .

Trouble with these steps? Read our troubleshooting guide. More detailed build guidance is available below.

Getting Help

Chat with us

Getting Help

If you have questions about the library, please be sure to check out the API documentation. If you still have questions, reach out to us on Slack or post a question on StackOverflow (with the libgit2 tag).

Reporting Bugs

Please open a GitHub Issue 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.

Reporting Security Issues

Please have a look at SECURITY.md.

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 for information

Conventions

See conventions for an overview of the external and internal API/coding conventions we use.

Building libgit2 - Using CMake

Building

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 2.8 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.

If you're not familiar with CMake, a more detailed explanation may be helpful.

Running Tests

Once built, you can run the tests from the build directory with the command

$ ctest -V

Alternatively you can run the test suite directly using,

$ ./libgit2_tests

Invoking the test suite directly is useful because it allows you to execute individual tests, or groups of tests using the -s flag. For example, to run the index tests:

$ ./libgit2_tests -sindex

To run a single test named index::racy::diff, which corresponds to the test function test_index_racy__diff:

$ ./libgit2_tests -sindex::racy::diff

The test suite will print a . for every passing test, and an F for any failing test. An S indicates that a test was skipped because it is not applicable to your platform or is particularly expensive.

Note: There should be no failing tests when you build an unmodified source tree from a release, or from the main branch. Please contact us or open an issue if you see test failures.

Installation

To install the library you can specify the install prefix by setting:

$ cmake .. -DCMAKE_INSTALL_PREFIX=/install/prefix
$ cmake --build . --target install

Advanced Usage

For more advanced use or questions about CMake please read https://cmake.org/Wiki/CMake_FAQ.

The following CMake variables are declared:

  • CMAKE_INSTALL_BINDIR: Where to install binaries to.
  • CMAKE_INSTALL_LIBDIR: Where to install libraries to.
  • CMAKE_INSTALL_INCLUDEDIR: Where to install headers to.
  • BUILD_SHARED_LIBS: Build libgit2 as a Shared Library (defaults to ON)
  • BUILD_TESTS: Build the unit and integration test suites (defaults to ON)
  • USE_THREADS: Build libgit2 with threading support (defaults to ON)

To list all build options and their current value, you can do the following:

# Create and set up a build directory
$ mkdir build
$ cmake ..
# List all build options and their values
$ cmake -L

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
  • LINK_WITH_STATIC_LIBRARIES: Link only with static versions of system 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.

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.

MinGW

If you want to build the library in MinGW environment with SSH support enabled, you may need to pass -DCMAKE_LIBRARY_PATH="${MINGW_PREFIX}/${MINGW_CHOST}/lib/" flag to CMake when configuring. This is because CMake cannot find the Win32 libraries in MinGW folders by default and you might see an error message stating that CMake could not resolve ws2_32 library during configuration.

Another option would be to install msys2-w32api-runtime package before configuring. This package installs the Win32 libraries into /usr/lib folder which is by default recognized as the library path by CMake. Please note though that this package is meant for MSYS subsystem which is different from MinGW.

Language Bindings

Here are the bindings to libgit2 that are currently available:

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" and "easy fix" that are good places to jump in and get started. There's much more detailed information in our list of outstanding projects.

Please be sure to check the contribution guidelines to understand our workflow, and the libgit2 coding conventions.

Download Details:

Author: libgit2
Source Code: https://github.com/libgit2/libgit2 
License: View license

#c #git #library #versioncontrols #hacktoberfest 

Madyson Reilly

Madyson Reilly

1604109000

Best Practices for Using Git

Git has become ubiquitous as the preferred version control system (VCS) used by developers. Using Git adds immense value especially for engineering teams where several developers work together since it becomes critical to have a system of integrating everyone’s code reliably.

But with every powerful tool, especially one that involves collaboration with others, it is better to establish conventions to follow lest we shoot ourselves in the foot.

At DeepSource, we’ve put together some guiding principles for our own team that make working with a VCS like Git easier. Here are 5 simple rules you can follow:

1. Make Clean, Single-Purpose Commits

Oftentimes programmers working on something get sidetracked into doing too many things when working on one particular thing — like when you are trying to fix one particular bug and you spot another one, and you can’t resist the urge to fix that as well. And another one. Soon, it snowballs and you end up with so many changes all going together in one commit.

This is problematic, and it is better to keep commits as small and focused as possible for many reasons, including:

  • It makes it easier for other people in the team to look at your change, making code reviews more efficient.
  • If the commit has to be rolled back completely, it’s far easier to do so.
  • It’s straightforward to track these changes with your ticketing system.

Additionally, it helps you mentally parse changes you’ve made using git log.

#open source #git #git basics #git tools #git best practices #git tutorials #git commit

Andreanne Kassulke

Andreanne Kassulke

1597916460

7 Best Practices in GIT for Your Code Quality

There is no doubt that Git plays a significant role in software development. It allows developers to work on the same code base at the same time. Still, developers struggle for code quality. Why? They fail to follow git best practices. In this post, I will explain seven core best practices of Git and a Bonus Section.

1. Atomic Commit

Committing something to Git means that you have changed your code and want to save these changes as a new trusted version.

Version control systems will not limit you in how you commit your code.

  • You can commit 1000 changes in one single commit.
  • Commit all the dll and other dependencies
  • Or you can check in broken code to your repository.

But is it good? Not quite.

Because you are compromising code quality, and it will take more time to review code. So overall, team productivity will be reduced. The best practice is to make an atomic commit.

When you do an atomic commit, you’re committing only one change. It might be across multiple files, but it’s one single change.

2. Clarity About What You Can (& Can’t) Commit

Many developers make some changes, then commit, then push. And I have seen many repositories with unwanted files like dll, pdf, etc.

You can ask two questions to yourself, before check-in your code into the repository

  1. Are you suppose to check-in all these files?
  2. Are they part of your source code?

You can simply use the .gitignore file to avoid unwanted files in the repository. If you are working on more then one repo, it’s easy to use a global .gitignore file (without adding or pushing). And .gitignore file adds clarity and helps you to keep your code clean. What you can commit, and it will automatically ignore the unwanted files like autogenerated files like .dll and .class, etc.

#git basics #git command #git ignore #git best practices #git tutorial for beginners #git tutorials

Loma Baumbach

Loma Baumbach

1601157360

Mirroring Git Changes From One Server to Another Server

Introduction

Hello all, nowadays most of the development teams using GIT version control, some of you may have a requirement of mirroring your team’s git changes from one server to another Git server. This article will help you to achieve the Git mirroring between one server to another server.

Business Case

I got one assignment wherein there will be 2 Git Servers, development will happen in one Git server and the changes should be synchronized to another Git server at regular intervals. But in my case, the complexity is both the servers are in different restricted network. So I have done the small experiment and it worked. And I am sharing the steps to you all in this article.

The Experiment Performed Using Below 2 GIT Servers

Main GIT Server: Let’s take our main git server is located in our office and can be accessed only in-office network.

**Mirror GIT Server: **The mirror server is located at the vendor/client-side, which can be accessible in a normal internet connection but not with our office network. Since the office proxy will block the outside URL’s.

#devops #git #git and github #git best practices #git cloning #git server

Rupert Beatty

Rupert Beatty

1617875220

Git Commands You Can Use To Dig Through Your Git History

In this short article, we’ll be exploring some quick  git commands that can help us in digging through our repositories’ history of commits. We’ll look at

  1. git log
  2. git shortlog
  3. git show
  4. git rev-list

#git #git-log #git-commands #git-history #aws