Baby-Git-rs

In 2005, Linus Torvalds published the germinal version of Git, which we called Baby-Git. Baby-Git could be thought of as a first rudimentary version of Git. Although much less sophisticated and convenient than its grown-up version, Baby-Git nevertheless encapsulates the core ideas behind modern-day Git. And this repo is the rust version of Baby-Git.

Components

1. Objects
   • Blob object
   • Tree object
   • Commit object
2. An object database
3. A current directory cache
4. A working directory

Build

# clone thie repo
git clone https://github.com/lancelot96/baby-git-rs.git
cd baby-git-rs
# build the source code using `cargo`
cargo build --release
# add the binary file to `$PATH` environment

Usage

There are 7 commands in Baby-Git, which basicly have the similar commands in Git.

Baby-Git		Git
init-db	---->	git init
update-cache	---->	git add
write-tree	---->	git write-tree
commit-tree	---->	git commit-tree
read-tree	---->	git read-tree
show-diff	---->	git diff
cat-file	---->	git cat-file

Preparation

$ cd examples
$ ls
hello.txt changelog
$ cat hello.txt
Hello world!
cat changelog
Initial commit.

Initialize the repository

$ baby-git init-db
defaulting to private storage area
$ ls .dircache
index objects

Add a file to the cache

baby-git update-cache hello.txt

Write a tree object to the object database

$ baby-git write-tree
1ddb3f3884ad449ab3d5f6dd4ba150d0f6eed6b3

Read a tree object

$ baby-git read-tree 1ddb3f3884ad449ab3d5f6dd4ba150d0f6eed6b3
100644 "hello.txt" (ae9a2591921ae106286b687f7fb0761b774bdb58)

Read the contents of a blob object

$ baby-git cat-file ae9a2591921ae106286b687f7fb0761b774bdb58
"temp_git_file_WmGVzA": blob
$ cat temp_git_file_WmGVzA
Hello world!

Commit a tree object to the repository

$ baby-git commit-tree 1ddb3f3884ad449ab3d5f6dd4ba150d0f6eed6b3 < changelog
Committing initial tree 1ddb3f3884ad449ab3d5f6dd4ba150d0f6eed6b3
2684fbe702307cff3e28ad17a9672bef466d9c80

Get the contents of a commit object

$ baby-git cat-file 2684fbe702307cff3e28ad17a9672bef466d9c80
"temp_git_file_yKopmM": commmit
$ cat temp_git_file_yKopmM
tree 1ddb3f3884ad449ab3d5f6dd4ba150d0f6eed6b3
author yuyy,,, <yuyy@yuyy-pc> 2021-03-14 03:46:01.437475755 UTC
committer yuyy,,, <yuyy@yuyy-pc> 2021-03-14 03:46:01.437475755 UTC

Initial commit.

Show the differences between blob objects and working files

$ baby-git show-diff
"hello.txt": ok
$ echo 'hello world!' > hello.txt
$ baby-git show-diff
"hello.txt": ae9a2591921ae106286b687f7fb0761b774bdb58
--- -   2021-03-14 11:51:03.513561514 +0800
+++ hello.txt   2021-03-14 11:50:56.916556320 +0800
@@ -1 +1 @@
-Hello world!
+hello world!

Parent commit objects

When committing a tree object using the commit-tree command, the user has the option of specifying parent commit objects. Logically, the parent commit object would be the commit object that resulted from the previous commit-tree command.

Branches

Parent commit objects can be used to create a branch in a repository. A branch can be created by specifying a parent commit object for a particular commit.

Merges

In Baby-Git, a merge of two branches can be performed by specifying the two parent commit objects of a commit object.

Database directory path

• SHA1_FILE_DIRECTORY environment to specify a custom directory that contains the object database

Commit environment variables

• COMMITTER_NAME to store the committer's name
• COMMITTER_EMAIL to store the committer's email address

Reference

• Baby Git Guidebook for Developers - Jacob Stopak
• The first version of Git