gitbean

A from-scratch, byte-compatible clone of Git's core plumbing commands, built in Java as a learning project.

Why

Building each command exactly like real Git (same object format, same .git-style layout) to understand version control internals deeply — not just approximate the behavior.

Setup: run gitbean from anywhere (recommended)

Add an alias so you can run gitbean <command> like a real installed tool, instead of retyping the full classpath every time.

Check your shell first:

echo $SHELL

Edit ~/.bashrc (or ~/.zshrc if using zsh) and add:

alias gitbean='java -cp ~/code/gitbean/target/classes com.kuwarte.gitbean.App'

Reload it:

source ~/.bashrc

Now gitbean init, gitbean add test.txt, etc. work from any directory.

Whenever you change the Java source, you still need to recompile first:

cd ~/code/gitbean && mvn compile

Without the alias

mvn compile exec:java -Dexec.mainClass="com.kuwarte.gitbean.App" -Dexec.args="<command> <args>"

Note: always chain compile before exec:java — Maven won't auto-recompile otherwise, and you'll silently run stale code.

Testing in a sandbox (important)

Never run gitbean commands directly inside the gitbean/ project folder — it creates a .gitbean/ folder and test files that clutter your actual source repo.

Instead, use a separate sandbox folder as a sibling to gitbean/:

~/code/
├── gitbean/     <- this repo (source code only)
└── sandbox/     <- test playground, separate git repo (or no repo at all)

mkdir -p ~/code/sandbox
cd ~/code/sandbox
echo "hello world" > test.txt
echo "second file" > test2.txt

gitbean init
gitbean hash-object -w test.txt
gitbean cat-file -p <hash>
gitbean add test.txt
cat .gitbean/index

Reset the sandbox to a clean slate anytime:

cd ~/code/sandbox
rm -rf .gitbean test.txt test2.txt

Commands implemented

Command	Description
init	Creates .gitbean/ repo structure
hash-object [-w] <file>	Hashes a file as a blob; -w also stores it
cat-file -p <hash>	Prints an object's content
cat-file -t <hash>	Prints an object's type
cat-file -s <hash>	Prints an object's size
add <file>	Hashes + stores a file as a blob, stages it in the index

Examples

gitbean init
gitbean hash-object -w test.txt
gitbean cat-file -p <hash>
gitbean add test.txt

Docs

• Progress / Milestone Checklist
• Object Format Reference
• Lessons Log