What are git internals

Git is a distributed version control system that is widely used in software development, version management and code collaboration. Because of the distributed nature of Git, every developer can perform code management and version control locally without being limited by server and network limitations. What are the internal mechanisms of Git?

The internal mechanism of Git mainly includes four aspects: objects, indexes, branches and references.

Object

The core mechanism of Git is the object, which is a basic unit for storing data. Git's database is organized into a tree structure called an "object library", which is stored in the local repository. Each object has a 40-character SHA-1 hash that Git uses to uniquely identify each object.

Git objects mainly include four types: blob, tree, commit and tag.

• Blob: It stores file content, and each file has a corresponding blob object.
• Tree: It stores the state of the file tree at each commit. Each tree object contains pointers to all related blob objects.
• Commit: It stores the metadata of a submission, including author, submission message, parent submission and other information. Each commit object points to a tree object, marking a specific version number.
• Tag: It is used to mark a certain submission, which is helpful for version management and release.

Index

Git internally maintains a data structure called "index", which is a cache area that records status changes between files and Git repositories. The index records the file name, modification time, size and other information of the current file, as well as a pointer to the blob object corresponding to each file. When a user modifies a file, Git automatically updates the index to better manage version changes.

Branch

Git internally maintains one or more pointers named "branch", each pointer points to a commit object, indicating the version of the current code. When a user creates a new commit, Git automatically creates a new commit object and updates the current pointer to that object.

Reference

In addition to branches, Git also supports another way to express versions, namely reference (ref). A reference is a more lightweight way to express a version, and it can point to any object, not just commit objects. Commonly used references include HEAD, tag, remote branch, etc.

Summary

These are the core components of Git’s internal mechanism. Understanding their internal structure can help developers better understand the behavior and implementation principles of Git, and better use Git for version control and collaboration.

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