Git: Книга от сообщества

Git Community Book

## Welcome to Git ##

Welcome to Git - the fast, distributed version control system.

This book is meant to be a starting point for people new to Git to learn it as quickly and easily as possible.

This book will start out by introducing you to the way Git stores data, to give you the context for why it is different than other VCS tools.

This is meant to take you about 20 minutes.

Next we will cover **Basic Git Usage** - the commands you will be using 90% of the time. These should give you a good basis to use Git comfortably for mostof what you're going to use it for. This section should take you about 30 minutes to read through.

Next we will go over **Intermediate Git Usage** - things that are slightly morecomplex, but may replace some of the basic commands you learned in the first section. This will mostly be tricks and commands that will feel more comfortable after you know the basic commands.

After you have all of that mastered, we will cover **Advanced Git** - commandsthat most people probably don't use very often, but can be very helpful incertain situations. Learning these commands should round out your day-to-daygit knowledge; you will be a master of the Git!

Now that you know Git, we will then cover **Working with Git**. Here we will goover how to use Git in scripts, with deployment tools, with editors and more.

These sections are meant to help you integrate Git into your environment.

Lastly, we will have a series of articles on **low-level documentation** that mayhelp the Git hackers who want to learn how the actual internals and protocols work in Git.

### Feedback and Contributing ###

At any point, if you see a mistake or want to contribute to the book, you can send me an email at [schacon@gmail.com](mailto:schacon@gmail.com), or you can clone the source of this book at

[http://github.com/schacon/gitbook](http://github.com/schacon/gitbook)

and send me a patch or a pull-request.

### References ###

Much of this book is pulled together from different sources and then added to.

If you would like to read some of the original articles or resources, please

visit them and thank the authors:

* [Git User Manual](http://www.kernel.org/pub/software/scm/git/docs/user-manual.html)

* [The Git Tutorial](http://www.kernel.org/pub/software/scm/git/docs/gittutorial.html)

* [The Git Tutorial pt 2](http://www.kernel.org/pub/software/scm/git/docs/gittutorial-2.html)

* ["My Git Workflow" blog post](http://osteele.com/archives/2008/05/my-git-workflow)

#Introduction

## The Git Object Model ##

### The SHA ###

All the information needed to represent the history of a project is stored in files referenced by a 40-digit "object name" that looks something like this:

6ff87c4664981e4397625791c8ea3bbb5f2279a3

You will see these 40-character strings all over the place in Git.

In each case the name is calculated by taking the SHA1 hash of the contents of the object. The SHA1 hash is a cryptographic hash function.

What that means to us is that it is virtually impossible to find two different objects with the same name. This has a number of advantages; among others: