Git

Version Control System

Git is a version control system. A version control system is a piece of software that helps the developers on a software team work together and also archives a complete history of their work.

There are three basic goals of a version control system:

1. people able to work simultaneously, not serially.
2. when people are working at the same time, their changes are not conflicting each other.
3. archive every version of everything that has ever existed — ever. And who did it. And when. And why.

Using Git

Using command line

Open Git Bash and try the following commands.

Change directory

bash
cd folder
cd folder/subfolder
cd ../
cd ../another-folder/nested-folder

bash
cd folder
cd folder/subfolder
cd ../
cd ../another-folder/nested-folder

Create file

bash
touch file-name.ext

bash
touch file-name.ext

Create directory

bash
mkdir folder-name

bash
mkdir folder-name

Remove file

bash
rm file-name.ext
rm folder

bash
rm file-name.ext
rm folder

Remove folder and all its contents (!)

bash
rm -rf folder

bash
rm -rf folder

Create a new, empty repository

repository = filesystem * time

bash
git init

bash
git init

The three states

Git has three main states that your files can reside in: committed, modified, and staged.

• Committed: the file is safely stored in repository
• Modified: the file is changed but not committed to repository yet
• Staged: the file is marked to go into your next commit snapshot

The diagram below illustrated the 3 states:

The basic workflow goes something like this:

1. You modify files in your working tree.
2. You selectively stage just those changes you want to be part of your next commit, which adds only those changes to the staging area.
3. You do a commit, which takes the files as they are in the staging area and stores that snapshot permanently to your Git directory.

To stage your change, we use the following command:

bash
git add <fileName>

bash
git add <fileName>

To commit all staged files, use the following command:

bash
git commit -m "<commit message>"

bash
git commit -m "<commit message>"

To check the current status:

bash
git status
git status -s

bash
git status
git status -s

To unstage a staged file:

bash
git reset HEAD <file-name>

bash
git reset HEAD <file-name>

Branching

When you create a git repo, by default you have one branch, and it is called master.

However, if multiple people working on same files together, their changes may conflict each other, and making everyone’s life difficult.

Branching means you diverge from the main line of development and continue to do work without messing with that main line.

To create a new branch

bash
git branch testing

bash
git branch testing

However, we’re still at master branch.

To switch to the new branch

bash
git switch testing

bash
git switch testing

Let’s modify something and do another commit.

Switch back to master branch

bash
git switch master

bash
git switch master

When you make another commit on master

You can merge changes of testing branch into master with:

bash
git merge testing

bash
git merge testing

Finally, you can delete a branch with

bash
git branch -D testing

bash
git branch -D testing

Images in this section are adapted from Pro Git

Using GitHub

Create a Repository

Pulling and Pushing from Repository

Forking and Pull Request

Fork and Create a PR to this repo.