GIT Development Log

Special thanks to Nikita for the excellent tutorial: https://www.leshenko.net/p/ugit

Resources

https://deepwiki.com/ReZeroS/git/1-overview

I've compiled useful reference materials in the ./doc directory. Additionally, these resources may be helpful:

• Nick Butler: A concise overview of diff algorithms
• jcoglan: Detailed explanation of the Myers diff algorithm
• Visualization: Helpful tool for visualizing and debugging diff algorithms
• PDF: A brief pdf about Git that you might find interesting

If you're interested in this project, feel free to share your ideas in the discussion forum or contact me via email.

Usage

0. alias zit='java -jar ../zit-1.0-SNAPSHOT-shaded.jar' - Create an alias for the zit executable

   • On Windows, add this to C:\Program Files\Git\etc\profile.d\aliases.sh

1. zit init - Initialize the .zit directory with an objects subdirectory, create an index file (staging area), and set up the default main branch

   • The default HEAD file contains: ref: ref/heads/main

2. zit hash-object file

   • Accepts a file path
   • Reads the file content
   • Hashes the content using SHA-1
   • Stores the file at .ugit/objects/{SHA-1-hash}

3. zit cat-file hash [object|tree|commit|...type] - Display file content

4. zit write-tree - Generate a tree structure representing the entire repository

   • Typically used after the add command to create a tree from the index file

5. zit read-tree hash

   • Warning: This will remove existing content before reading
   • Use cat-file to locate the root tree
   • write-tree logs can also help identify all trees

6. While write-tree captures snapshots, it lacks contextual information. Use zit commit -m "message" for proper versioning

   • Check commit content with cat-file hash commit-id
   • HEAD records commits with parent information

7. Use log to view commit history after making commits

8. Checkout: Select a commit ID from log to restore that state

   • [Fixed with getBytes(Charsets.UTF_8)] Bug: Chinese file/directory names previously displayed incorrectly
   • Accepts head alias, hash, or ref (branch, tags, HEAD, etc.)

9. tag creates an alias for a commit ID, introducing a core Git concept

   • The git-ref documentation provides essential reference knowledge

10. TODO: Implement zit lg graph visualization using Graphviz

11. zit branch name [id] - Create branches as in standard Git

    • All refs under refs/heads are treated as branches
    • File content is simply the commit ID, defaulting to HEAD

12. zit show displays detailed changes using diff, while status shows summary information

13. zit add stages files or directories in .zit/index

14. zit commit invokes write-tree and updates the HEAD pointer to the new commit ID

    • First use creates the default main branch and updates HEAD
    • Removes MERGE_HEAD and includes message in commit

15. zit status shows the current repository state

    • Displays current branch (unless in detached HEAD state)
    • Shows merge hash ID during merge operations
    • Lists changes to be committed (diff between HEAD tree and index)
    • Lists unstaged changes (diff between index and working tree)

16. zit diff implements the Myers diff algorithm without linear space refinement

17. zit reset moves HEAD to the specified commit (difference from checkout pending implementation)

18. zit merge checks if the merge base equals HEAD, using fast-forward merge when possible

    • Fast-forward requires no additional commit
    • Otherwise uses diff3 to merge the base, HEAD tree, and other tree
    • Leaves merge_head in the zit root directory, requiring manual commit
    • zit merge-base helps find the common ancestor commit for merging and debugging

19. zit fetch and zit push download/upload objects and update references

Summary

UPDATED 2021.02.21

• Implemented diff (Myers algorithm without linear space optimization) and merge (simple diff3) algorithms instead of relying on Unix tools
• While Ugit uses Pythonic code, zit aims to provide code that's easily understandable for developers from various language backgrounds

TODO

1. Enhance git hash-object to match real Git behavior:
   • Write object size to file
   • Compress objects
   • Distribute objects across 256 directories to avoid performance issues with large file counts