Are the implementation principles of git and svn the same?

The implementation principles of git and svn are different; git is a distributed version control system, svn is not. This is the core difference between git and svn non-distributed version control systems. It is stored in metadata mode, while svn is stored in file mode.

The operating environment of this article: Windows 10 system, Git version 2.30.0, Dell G3 computer.

Are the implementation principles of git and svn the same?

Git is an open source distributed version control system used to handle any problem quickly and efficiently. Projects small or large.

Git is an open source version control software developed by Linus Torvalds to help manage Linux kernel development.

Git is different from commonly used version control tools such as CVS and Subversion. It uses a distributed version library and does not require server-side software support.

1. The difference between Git and SVN

GIT is not only a version control system, it is also a content management system (CMS), work management system, etc.

If you are a person with a background in using SVN, you need to make certain ideological changes to adapt to some concepts and features provided by GIT.

Differences between Git and SVN:

• 1. GIT is distributed, SVN is not: this is GIT and other non-distributed version control systems, such as SVN , CVS, etc., the core difference.

• 2. GIT stores content as metadata, while SVN stores content as files: all resource control systems hide the metainformation of files in a file similar to .svn, .cvs etc. folder.

• 3. GIT branches are different from SVN branches: branches are not special at all in SVN, they are just another directory in the repository.

• 4. GIT does not have a global version number, but SVN does: So far, this is the biggest feature that GIT lacks compared to SVN.

• 5. The content integrity of GIT is better than that of SVN: GIT's content storage uses the SHA-1 hash algorithm. This ensures the integrity of code content and reduces disruption to the repository in the event of disk failures and network problems.

2. Git principle: Git workspace, temporary storage area and version library

Basic concepts

Let’s start with Understand the concepts of Git workspace, staging area and repository

Workspace: It is the directory you can see on your computer.

Temporary storage area: called stage, or index in English. It is generally stored in the index file (.git/index) under the ".git directory", so we sometimes call the temporary storage area the index (index).

Repository: There is a hidden directory .git in the workspace. This is not the workspace, but the Git repository.

The following figure shows the relationship between the work area, the staging area in the repository and the repository:

The left side of the figure is the work area, with the version library on the right. The area marked "index" in the repository is the staging area (stage, index), and the area marked "master" is the directory tree represented by the master branch.

From the picture we can see that "HEAD" is actually a "cursor" pointing to the master branch. Therefore, where HEAD appears in the command shown in the figure, it can be replaced with master.

The area identified by objects in the figure is the Git object library, which is actually located in the ".git/objects" directory, which contains various created objects and content.

When the "git add" command is executed on a file modified (or added) in the workspace, the directory tree of the temporary storage area is updated, and the contents of the file modified (or added) in the workspace are written. to a new object in the object library, and the object's ID is recorded in the file index of the temporary storage area.

When performing a commit operation (git commit), the directory tree in the temporary storage area is written to the version library (object library), and the master branch will be updated accordingly. That is, the directory tree pointed by master is the directory tree of the temporary storage area at the time of submission.

When the "git reset HEAD" command is executed, the directory tree in the staging area will be rewritten and replaced by the directory tree pointed to by the master branch, but the workspace will not be affected.

When the "git rm --cached " command is executed, the file will be deleted directly from the temporary storage area, and the workspace will not be changed.

When the "git checkout ." or "git checkout -- " command is executed, the files in the workspace will be replaced with all or specified files in the temporary storage area. This operation is dangerous and will clear changes in the workspace that have not been added to the staging area.

When the "git checkout HEAD ." or "git checkout HEAD " command is executed, all or part of the files in the master branch pointed to by HEAD will be used to replace the staging area and the workspace. document. This command is also extremely dangerous, because it will not only clear the uncommitted changes in the workspace, but also clear the uncommitted changes in the staging area.

Recommended learning: "Git Tutorial"

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