How does git ensure data redundancy?

Git is a version control system created by Linus Torvalds in 2005. Git, with its efficient distributed version control system, has become one of the most popular source code management tools currently. In Git, data redundancy is a very important feature, and it is implemented through object storage and hashing algorithms.

1. Object Storage

In Git, each version of data is stored as an object, called a "Git object". These objects include files, code, history, etc. All Git objects are stored in a place called the "object library". Object libraries usually contain three types of objects: blob objects, tree objects and commit objects.

Blob object is the most basic object type in Git, which represents files. When we edit a file and add it to a Git repository, Git converts the file into a blob object and stores it in the object library. This way, each version of the file has a unique SHA-1 hash value corresponding to it, so even if the content is modified, a new blob object will be generated.

Tree object is also called a folder, which is a list containing multiple blob objects and other tree objects. Each tree object represents a folder and contains all blob objects and tree objects of subfolders under the folder. In this way, each version of the folder has a unique SHA-1 hash value corresponding to it.

The Commit object contains submission-related information, such as author, timestamp, submission instructions, etc. Each commit has a unique SHA-1 hash corresponding to it. When a commit is made, Git will create a new commit object and use the current tree object as a snapshot. This commit object will contain the SHA-1 value of the previous commit object, thus forming a timeline, thus retaining all historical versions.

2. Hash algorithm

Git uses the SHA-1 hash algorithm to prevent accidental loss or tampering of data. The SHA-1 algorithm is very similar to the MD5 algorithm, which converts input data of any length into a 160-bit hash value and produces a unique hash value in any case.

When we add a new blob object or tree object to Git, Git calculates its hash value based on the SHA-1 algorithm. Git will then use the hash value as the file name and save the object in the ".git/objects" directory. Since the SHA-1 algorithm is irreversible, each Git object has a unique SHA-1 value that is closely related to its content.

Every time a folder or file is modified, Git will calculate the SHA-1 hash value of the new folder or file and add it to the object library as a new blob object or tree object. middle. This ensures the integrity of historical versions and data redundancy. Even if an object is accidentally deleted, the original object can be retrieved through the hash value.

Summary

Git's data redundancy is achieved through object storage and hash algorithms. Using object storage allows Git to store all version data in an efficient and flexible way, and ensure the uniqueness of object hash values ​​through the hash algorithm. This method ensures that all data in the Git warehouse can be prevented from being lost or tampered with, thereby ensuring the integrity and security of version data.

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