Git implementation from scratch

Friday. February 18, 2022

Python Git Implementation

Implementation of the Git version control system from scratch, written purely in Python.
Check the github repository here: Git Implementation

Implements the following fundamental features of git:

• add
• cat-file
• checkout
• commit
• hash-object
• init
• log
• ls-tree
• merge
• rebase
• rev-parse
• rm
• show-ref
• tag

Structure

• GitRepository:
  • Object representing a git repository.
  • GitRepository consists of two things:
    • worktree - a “work tree”, where the files meant to be in version control live.
    • gitdir - “git directory”, where Git stores its own data.
• GitObject:
  • Objects are of multiple types, and they all share the same storage/retrieval mechanism and the same general header format.
  • GitObject is a generic object with two unimplemented methods:
    • serialize()
    • deserialize()
• GitBlob:
  • Blobs are user content: every file you put in git is stored as a blob.
  • The serialize and deserialize functions store and return their input unmodified.
• GitCommit:
  • GitCommit object (uncompressed, without headers) begins with a series of key-value pairs, with space as the key/value separator, and ends with the commit message, that may span over multiple lines.
  • Values may continue over multiple lines, subsequent lines start with a space which the parser must drop.
  • GitCommit fields:
    • tree is a reference to a tree object.
    • parent is a reference to the parent of this commit.
    • author and committer are separate, because the author of a commit is not necessarily the person who can commit it
    • gpgsig is the PGP signature of this object.

License

Distributed under the MIT License. See LICENSE.md for more information.

References

• https://git-scm.com/docs/gitrepository-layout
• https://git-scm.com/book/en/v2/Git-Internals-Git-Objects
• https://www.freecodecamp.org/news/git-internals-objects-branches-create-repo/