Git Basics

🔷 Version Control

Open source

• Anyone can download and suggest changes.

Linux

• a major open source
• Thousands of regular developers, millions of files
• Developers spread over the globe across multiple time zones

Version Control System

• Manage these things using a version control system (VCS)
• A version control system allows for the management of a code base.

Repository 레포지토리

• Repository : a location storing a copy of all files.
  • You don't edit files directly in the repo
  • You edit a local working copy or working tree
  • You commit your edited files into the repo

• Files in your working directory must be added to the repo in order to be tracked.

What to put in a Repo?

• Source code (Ex: .java, .c, .h, .cpp)
• Build configuration files (Makefile, build.xml)
• Other resources : icons, text etc.

• Things generally NOT put in a repo
  • Object files (.o)
  • Executables (.exe)

More Uses of Version Control

• VCS is essential for quality source code development

• Undo changes to a file

  • Like "undo" in an editor
  • Keep the whole history of every file and a changelog

• Who changed what, when

Essential features

• Check-in and Check-out (Upload/Download) of items to repository
• Creation of baselines (labels/tags)
  • Version 1.0 released!
• Control and manipulation of branching
  • management of multiple versions
• Overview of version history

1. Centrallized Version Control
   • A single server holds the code base
   • Code is shared by check-in/check-outs
   • CVS, Subversion, Visual Source Safe
   • Advantage
     • Easier to maintain a single server
   • Disadvantage
     • Single point of failure.

2. Distributed Version Control
   • Each client holds a complete copy of the code base.
   • Code is shared by push/pulls
   • Advantages
     • Many to operations cheaper
     • No single point of failure
   • Disadvantages
     • A bit more complicated!

🔷 Git

Git Advantages

• Resilence
  : Distributed multiple repositories
• Speed
  : Very fast operations compared to other VCS
• Space
  • Compression can be done across repository not just per file
  • Minimizes local size as well as push/pull data transfers
• Simplicity
  : Object model is very simple
• Large userbase

Git Disadvantages

• Learning Curve
  • Hard to learn
  • Comceptual difference from centralized version control
  • Huge amount of commands

A Local Git project has three areas

1. Working directory

• Sometimes called the "working tree"
• The area where you are currently working (Your files)

2. Staging Area

• Also known as the "index"
• Tracking and savings changes
• Prepare for a commit
• Stored in .git/index

3. Repository (local)

• Commits, branches and other things are stored in the repository
• Everything in your .git directory

Git file lifecycle

Basic Flow

1. Init clone a repo
2. Edit files
3. Stage the changes
4. Review your changes
5. Commit the changes

git init
git clone "ssh or http of git repo"
# file editing ...
git status
git add file.txt
git rm file.txt
git commit -m "commit message"
git push

git init 을 통해 local 폴더에서 git을 시작.
git clone 을 통해 local 폴더와 연결할 git의 repository의 주소를 입력하여 연결.
로컬에서 파일을 수정한 후 git status 를 입력하면 local 폴더에서 아직 stage에 올라가지 못한 변경사항이 있는 파일들을 보여줌.
git add 명령어를 통해 그러한 파일들을 stage에 올려줌. git add filename.확장자를 입력해준다. 만약 모든 변경 된 파일을 올려주고 싶다면 git add *를 입력.
git rm 명령어는 add한 file을 지우고 싶을 때 사용.
git commit 명령어는 스테이지에 있는 파일들을 repository로 올려줌. 이 때, 커밋 메세지를 함께 입력해야하는데, 만약 커밋 메세지로 "Version updated"를 작성하고 싶다면, 두 가지 방법이 있다.
git commit -m "Version updated" 를 git bash에 입력하거나, git commit을 입력하면 텍스트파일이 뜨는데 거기에 "Version updated"를 적고 창을 닫으면 된다.

여기까지가 기본적인 git 의 명령어이고, 그 밖의 명령어는 다음과 같다.
git diff : working directory 와 stage의 차이점을 보여줌.
git diff -cached : stage와 repository의 차이점을 보여줌.
git log : 지금까지 history를 보여줌.