This document provides an overview of Git and GitHub, including basic command line commands, version control systems, Git workflow, setting up Git and GitHub, differences between Git and GitHub, common Git commands like clone, init, remote, branch, merge, rebase, and undoing changes. It explains key concepts like the three tiers of Git (working directory, staging area, repository), HEAD pointer, forking and pull requests.

1. Git and GitHub

2. Let’s start from the basics: Using command line
● To check the contents of the current directory
○ Linux: ls
○ Windows: dir
● To copy a file from source path to destination path
○ Linux: cp source-path destination-path
○ Windows: copy source-path destination-path
● To move a file from source path to destination path
○ Linux: mv source-path destination-path
○ Windows: move source-path destination-path
● To go back to the previous directory
○ Linux: cd ..
○ Windows: cd
● To create a new file
○ Linux: touch filename
○ Windows: notepad filename
● To create a directory
○ mkdir

3. Command line - Continued
● To delete a file
○ Linux: rm filename
○ Windows: del filename
● To delete a directory
○ rmdir
● To get the current directory path
○ Linux: pwd
○ Windows: chdir
● To get information about any command
○ Linux: man <command>
○ Windows: <command> /?
● To rename an existing file
○ Linux: mv old_filename new_filename
○ Windows: rename old_filename new_filename
● To exit command line
○ Linux: exit
○ Windows: exit

4. Version Control System
● Software tool to helps record changes to files by keeping a track of
modifications done to the code
● Multiple people can simultaneously work on a single project
● You can work on your project from various systems
● Access to historical version of the project
● Repository: Database of changes. Contains all edits and historical versions of
the project

5. Types of Version Control Systems
● Centralised VCS
● Distributed VCS

6. Centralized Version Control System
● One central remote repository
● Users make changes locally and
commit to the central repository
● To get the latest content from the
remote repository, users have to
update.
● Drawbacks: If the central repository is
corrupted, information is lost.

7. Distributed Version Control System
● Repository is distributed and is present with
each user.
● Users make changes to the code and
commit to their local repositories.
● For the code to be accessible to others, users
have to push the code after committing to
their local repositories.
● Since the previous versions of the code files
exist with all the users on their local
repositories, in case of failure of one system,
data is not lost.

8. Git
● Distributed Version Control System
● Free and Open Source - source code: https://github.com/git/git
● Allows a team of people to work together
● Works by taking snapshot of files
● Can be used to track changes in a set of files
● You can use Git without GitHub

9. Git Workflow - 3 tier architecture
● Working directory, staging index/
staging area and repository are all
present on our system.
● git add -> adds the changes to
staging area
● git commit -> commits the
changes from staging area to the
repository

10. Setting up Git and GitHub
Setting RSA key-pair:
1. Run “ssh-keygen” in terminal.
2. Run “cat .ssh/id_rsa.sh” and copy the rsa key.
3. Paste the public key in your github account by going to settings.
Setting your username and email in local system:
1. git config --global user.name “your username”
2. git config --global user.email “youremail@gmail.com”

11. Difference between Git and GitHub
GitHub is platform which uses Git to communicate with our local system.
In other words, Git is a TOOL and Github is a PLATFORM.

12. Git Clone
● git clone -> used to make a clone/ copy of an existing repo in a new directory, at
another location
● Automatically creates a remote connection “origin” to the original repo

13. Creating a GitHub Repository - Cloning
● Go to github.com and login with your credentials
● Click on New to create a new repository, give it a name and click on Create
Repository.
● Optionally you can add a description for the repository
● Click on Clone and Download button and copy the repo URL
● On your command line, navigate to the path where you would like to place the
project and clone the created repository:
git clone <url>
● Move inside the cloned repository:
cd reponame

14. Git Init
● Creates a new Git repository
● If you already have a project, no other Git command will work on it unless you
execute this command on the project directory
● After executing the command, .git subdirectory would be created with all the
required metadata

15. Creating a GitHub Repository - Init
● Create a project on local system
○ cd project_name
○ git init
● Go to GitHub and create a new repo
● Copy the https URL of the repo
● Create an instance of remote URL on local system
○ git remote add origin <URL>
○ git pull origin master
● Create a new branch to make your changes
○ Git checkout -b <branch_name>
● Create a new file
○ touch filename
● Commit and push the changes
○ Git add .
○ Git commit -m “”
○ Git push origin branch_name
● Go to GitHub and create a PR

16. Git Remote
● Used to reference a remote repository
● While forking you were working with a remote repository so you had to create
the remote reference
● origin is the default remote reference created when you clone a repository
● When using git init on a local directory, you have to create the remote reference
to whichever repo you want the directory to point to

17. Git Remote Commands
● Adding a remote reference
○ git remote add <remote_reference_name> <URL>
● To list all the references stored by the repository using one of the below
commands
○ git remote -v
○ git remote -verbose
● To remove a reference
○ git remote rm <reference_name>
● To rename an existing remote reference
○ git remote rename <old_name> <new_name>
● To get more information about any existing remote reference
○ git remote show origin

18. Git Branching
● Diverge from main line of code and make changes to the separate line (branch)
without messing with the main line

19. Creating a new branch
git branch testing

20. HEAD Pointer
● By default points to the latest
commit on the branch
● Switches when you switch the
branch
● If you go back to master
branch from testing branch,
HEAD will point to the
master again

21. ● You can move across the
commits and the HEAD will
move accordingly in the branch.
HEAD Pointer - Moving in a Branch

22. HEAD Pointer - Moving across Branches
● If you switch to the testing
branch, HEAD will point the
last commit of testing branch

23. Committing to the new branch
● If you execute on testing
branch
○ git commit -m “message”
● The HEAD has now moved to
the new commit on testing
branch
● You create a pull request in
order to be able to merge your
branch (testing) to the master
branch
● After merge, the master and
testing branch will both point
to the latest commit i.e. ‘87ab2’
in this case

24. Git Branches & Pull Requests
● Create a new branch
○ git checkout -b branch-name
● Command to list down the branches
○ git branch
● Command to switch from one existing branch to another
○ git checkout branch_name
● Make your changes in the new branch
○ git add filename
○ git commit -m “message”
○ Git push origin master
● After pushing go to your repo and create pull request.

25. Forking - Working on someone else’s repo
● Go to https://github.com/girlscript-blr/codewithgirlscriptblr and fork the project
● Go to the forked repo present in your GitHub account and copy the repo https
URL
● Clone the repo in your local system
○ git clone <URL>
● Add https://github.com/girlscript-blr/codewithgirlscriptblr as a remote URL
○ git remote add upstream https://github.com/girlscript-blr/codewithgirlscriptblr
● Create a new branch for your changes
○ git checkout -b <branch_name>
● Create a new file/edit any existing file
● Commit and push the changes
● Create a PR on GitHub

26. Git Merge

28. Fast Forward vs True Merge
Fast Forward Merge True Merge

29. Merge Conflicts

30. Git Log
● Command to view the commit history in reverse order
○ git log
● Hash is unique to each commit and depends on the contents modified in the
commit as well as the author of the commit
● Git log will provide with the commit id, author’s name, email, date and commit
message of each commit
● To view only a certain number of past commits - below command will display last
2 commits
○ git log -p -2

31. Git Commit Id
● Generates a checksum for each
commit
● Checksum -> algorithm run on
some data
● Remains unique for all commits
● Data -> all the changes made in
the commit, author of the
commit, commit message and
some other metadata

32. Undoing in Git
● Modifying the last commit
○ To either add more files to the last successful commit or change the commit message
■ git commit --amend
● Unstaging a staged file
○ Once you perform git add . the files are added to the staging area
○ In order to remove a certain file from the staging area
■ git restore --staged file_name
● Reverting the last commit
○ To delete the last commit from staging area but still have changes in working directory
■ git reset --soft HEAD~1
○ To delete the last commit and also the changes from working directory
■ git reset --hard HEAD~1
○ Default one
■ git reset --mixed HEAD~1

33. Cherry Picking in Git

34. Git Rebase

35. Merging vs Rebasing

36. Merging vs Rebsing