So, what is Git in a nutshell? This is an important section to absorb, because if you understand what Git is and the fundamentals of how it works, then using Git. The second edition of this book is meant to address those example of Git hosting, I have decided to turn that part of the book into more. Access this book for free. ISBN ; This book is an open access book, you can download it for free on Softcover 44,95 €.

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Git on the Server 4. This is a character string composed of hexadecimal characters 0—9 and a—f and calculated based on the contents of a file or directory structure in Git.

Conceptually, most other systems store information as a list of file-based changes. This is an important distinction between Git and nearly all other VCSs.

Committed means that the data is safely stored in your local database. These files are pulled out of the compressed database in the Git directory and placed on disk for you to use or modify. In many other systems, doing so is either impossible or painful. Git in Other Environments A1. It makes Git reconsider almost every aspect of version control that most other systems copied from the previous generation. A SHA-1 hash looks something like this:.

Modified means that you have changed the file but have not committed it to your database yet.

Git – Git Basics

If you want to see the changes introduced between the current version of a file and the file a month ago, Git can look up the file a month ago and do a local difference calculation, instead of having to either ask a remote server to do it or pull an older version of the file from the remote server to do it locally. Git is a member of Software Freedom Conservancy, which handles legal and financial needs for the project. The mechanism that Git uses for this checksumming is called a SHA-1 hash.


And if it was changed since it was checked out but has not been staged, it is modified. The staging area is a file, generally contained in your Git directory, that stores information about what will go into your next commit.

It is hard to get the system to do anything that is not undoable or to make it erase data in any way. This may not seem like a huge deal, but you may be surprised what a big difference it can make. Staged means that you have marked a modified file in its current version to go into your next commit snapshot. A SHA-1 hash looks something like this: Embedding Git in your Applications A2.

Pro Git, Second Edition

If you get on an airplane or a train and want to do a little work, you can commit happily to your local copy, remember? If it has been modified and was added to the staging area, it is staged. This is the most important part of Git, and it is what is copied when you bok a repository from another computer.

The Git directory is where Git stores the metadata and object database for your project. When you do actions in Git, nearly all of them only add data to the Git database.

Instead, Git thinks of its data more like a series of snapshots of a miniature filesystem. This is an important section to absorb, because if you understand what Git is and the fundamentals of how it works, then using Git effectively will probably be much easier for you. This makes Git more like a mini filesystem with some incredibly powerful tools built on top of it, rather than simply a VCS.

You do a commit, which takes the files as they are in the staging area and stores that snapshot permanently to your Git directory. Everything in Git is checksummed before it is stored and is then referred to by that checksum.

This means you see the project history almost instantly. With Git, every time you commit, or save the state of your project, Git basically takes a picture of what all your files look like at that moment and stores a reference to that snapshot.


Git thinks about its data more like a stream of snapshots.

1.3 Getting Started – Git Basics

Because you have the entire history of the project right there on your local disk, most operations seem almost instantaneous. Git has three main states that your files can reside in: This functionality is built into Git at the lowest levels and is integral to its philosophy.

Git and Other Systems 9. For a more in-depth look at how Git stores its data and how you can recover data that seems lost, see Undoing Things. You modify files in your working tree. In booj, Git stores everything in its database not by file name but by the hash value of its contents. So, what is Git in a nutshell?

This leads us to the three main sections of boko Git project: These other systems CVS, Subversion, Perforce, Bazaar, and so on think of the information they store bookk a set of files and the changes made to each file over time this is commonly described as delta-based version control.

Conservancy is currently raising funds to continue their mission. You selectively stage just those changes you want to be part of your next commit, which adds only those changes to the staging area. The major difference between Git and any other VCS Subversion and friends included is the way Git thinks about its data. You will see these hash values bokk over the place in Git because it uses them so much.

The working tree is a single checkout of one version of the project. Git Has Integrity Everything in Git is checksummed before it is stored and is then referred to by that checksum.