This is a simple Git library implemented in Kotlin, providing basic Git functionality. The library includes three main entities: Blob, Tree, and Commit. The implementation aims to mimic the essential features of Git, with a focus on simplicity and avoiding data redundancy.

The Blob represents a piece of data stored as a string. It includes a SHA-1 hash for unique identification.

val git = Git()
val data = "some data"
val blob = git.blob(data)
prinln(blob.hash())  

The Tree acts as a container for a collection of named blobs or other trees. It has a SHA-1 hash that uniquely identifies the tree. Trees can be modified by adding or removing objects, and once locked(see below in Commit), no further modifications are allowed.

val tree = git.tree()
tree.add(blob)
tree.remove(blob)

val anotherTree = git.tree()
tree.add(anotherTree)
tree.remove(anotherTree)

The Commit serves as a pointer to the main Tree object and stores metadata related to the commit. Metadata includes the author, commit message, commit time, and the SHA-1 hash of the commit itself. Commits are stored chronologically, allowing tracking of their relationships.

val commit = git.commit(tree, "message", "author")
val anotherBlob = git.blob("another data")
tree.add(anotherBlob) // error

anotherTree.add(anotherBlob)
val anotherCommit = git.commit(anotherTree, "another message", "author")

println(anotherCommit.parent == commit) // true

The Branch serves as a pointer to the last commit, adding the possibility to create a new sequence of commits. Users can switch between branches to manage different lines of development. When instance of Git is created, head is set to the Branch with name "master"

println(git.getHead().getName() == "master") // true

val branch = git.branch("test")

println(git.getHead().getName() == "test") // false

The library allows the creation of new commits by specifying a tree, commit message, and author.

val commit = git.commit(tree, message, author)

The library provides a log function to list commits based on optional filtering criteria such as hash, message, and author.

git.log(hash = hash, message = message, author = author)

The library includes functions (findByHash, findByMessage, findByAuthor) to search for a specific commit based on hash, message, or author.

val commit1 = git.findByHash(hash)
val commit2 = git.findByMesssage(message)
val commit3 = git.findByAuthor(author)

The library allows to switch between branches using their names

val branch = git.branch("test")
git.checkout("test")

println(git.getHead() == branch) // true