GitThe fast version control system

Version Control System

• Allows to track changes to files

• Provides repository of changes

• Consists working directory / current state

• VCS can be:• Centralized (Ex: SVN, CVS)

• Server: single database• Clent: working directory and state.

• Decentralized(Ex: BitKeeper, Mercurial, Git)

What is Git?

• free & open source

• distributed version control system • Anyone can be the server• Repository coupled with working directory• Complete history• Disconnected operation• No single point of failure

• Designed to be fast and efficient for small and very large size projects

Git history

• 2002• Linus Torvalds decided to use BitKeeper for

tracking Linux kernel development• Linux development scales better

• 2005• BitMover dropped free license• Linus writes his own VCS, Git

Getting started with Git

• yum install git-core

• git clone --help

• git config --global user.name ‘Keshavaprasad B S’

• git config --global user.email kbsbng@gmail.com

Getting started with Git

• Creating new git repo:• git init

• git add

• git commit

• Cloning from existing repo:• man git-clone

Git config

• Types• $(prefix)/etc/gitconfig --> system• ~/.gitconfig --> global• .git/config --> local

• Aliases

Concept of working directory, index and repository

• git add -> adds stuff to index

• git commit -> commits stuff from index to repository

• git diff -> diff between working tree and index

• git diff --cached -> diff between HEAD and repository

Concept of working directory, index and repository

• git fetch-> fetch the code from remote repo to local

• git pull -> pulls code from remote to local and w.d.

• git checkout -> checkout code from local repo to w.d.

Git object model

• All the information needed to represent the history of a project is stored in files referenced by a 40-digit SHA1 hash.

• Each object consists of type, size and contents.

• 4 types of objects• Blob – stores files data (generally a file)• Tree – consists bunch of other trees or blobs (files

and subdirectories)• Commit – points to a single tree. Contains meta of

author, timestamp, pointer to prev. commit etc.• Tag – Marks a specific commit

Git object model

• Git show <sha>

gitk and git log

• Install gitk

• git log --pretty=oneline

• git log --pretty=format:'%h : %s' --topo-order –graph

• git log --no-merges

• git log --stat

Git branches

• git clone git@github.com:kbsbng/try_git.git

• git branch hack-1

• Make changes and commit to branch and master

• git rebase master hack-1

• git merge hack-1

Git merge/rebase

1. git checkout -b mywork origin

3a. git pull

3b. git pull --rebase

Git tags

• Lighweight tags (branch that never moves)• git tag stable-1 <commit>

• Tag Objects• Can include comments / signature• git tag –a stable-1 <commit>

Stashes

• git stash save “WIP for foo feature”

• git stash apply

• git stash list

Some tips

• Git grep can be used search through previous versions of a project without checking them out.

• master@{yesterday} refers to where the master branch was yesterday.

Git vs svn

• Cheap local branching

• Everything is Local

• Fast

• Git is small

• Provides staging area

• Distributed

• Any workflow

• Github

References

• http://book.git-scm.com/

• http://whygitisbetterthanx.com

Thank you