Git & GitHub Introduction

Git :

Git is fast, easy to learn, distributed version control system created by Linus Torvalds: The man who created Linux operating system. Git was originally created for managing & developing Linux kernel software. Many large IT players like Google, Netflix, Twitter, Facebook are using Git for managing their key projects and it’s extremely popular among developers. Git is platform, file type and programming language independent. 

Traditional code repositories like CVS keeps single central repo but Git provides a local copy of repo to each developer while maintaining a remote central master repo. Local repo can be synced and push changes to remote repo as and when required.

https://git-scm.com/

GitHub:

GitHub is Git repository hosting service, owned by Microsoft since 2018. Basically, it is central or remote repository where all Git projects created in developers’ machine can be hosted for sharing with large audiences. It is largest host of source code in the world at the moment.

Key Concepts:

Team will use a central repo for collecting all changes – called the ‘remote’ repo’.

GitHub is typically the remote repo host. It is available at - https://github.com/

Provides communication collaboration tools and repo hosting

Provides proven and effective workflow for contributors.

Workflow:

1.     Set up Git and GitHub on local machine.

2.     Initialize Git in local machine.

3.     Clone a remote repo from GitHub and create a local copy.

4.     This local repo branch will be used by developers to work on.

5.     Developer creates new file and change existing file in project.

6.     Commits new changes locally in his machine.

7.     Then developer pushes changes to remote repo.

8.     Developer performs a Pull request.

9.     Changes are then reviewed by remote repo owner and he accepts or deny.

10.   If accepted, new changes are merged into remote trunk.

11.   If denied, developer makes improvements and pushes again.

12.  Before pushing local changes, developer must perform remote pull so he has latest of remote repo.

Another example of Git repository is GitLab: https://about.gitlab.com/

But this blog covers GitHub only.

Setting up Git and GitHub:

Step1: Download Git or check in your machine if you already have Git installed (for those using Mac you may have Apple git already provided).

$ Git --version     OR    $ Git version 

Note: For those Windows OS, all Git commands will remain same. As you will be using GitBash – Provided by Git when you install from https://git-scm.com/

Step2: For detailed instructions on how to setup and use GitHub you may also watch my you-tube blog:   https://www.youtube.com/watch?v=PRz0o-eYvCM&t=10s

Step 3:  Key Git Commands

$ git init	Sets up a project directory for working with Git
$ git config
$ git add	Adds a file to Git’s index (staging area) so it can be tracked
$ git status	Provides report of staging area content and committed content
$ git commit	Moves staged files into local history
$ git push	Copies local changes to a remote repo
$ git pull	Copies changes in a remote repo to a local rep/
$ git clone	Copies an entire project from a remote repo to create a local repo

Step 4: Command CheatSheet

$ git version or $ git --version	To check git version installed
$ git init	Use this command on new project folder which you want to make a local repo. This will initialise git on this location and creates a hidden directory called ‘.git’
$ git config - - global user.name  “github user name” $ git config - - global user.email  “test@gmail.com”	This is metadata that will be used by other git commands to track changes by user details. Due to use of – global keyword , user details will be applicable to all github projects in this machine.
$ git clone “Remote repo URL”	Clones a remote repo using its GitHub URL
$ git status	Provides details of changes in local repo vs remote repo
$ git add .  or   $ git add “filename or file name with wildcard chars” e.g. *.java, *.js	Adds changes to local repo’s staging area
$ git rm “file name”	Removes a file from a staging area so its no longer tracked
$ git commit -m “any comments..”	Commits changes to local repo. Comments are mandatory.
$ git remote add origin “HTTPS URL of github repo”	This will ask for user name & password of your GitHub account. This is pre-requisite before you push your local repo to a remote repo whose URL is used in command.
$ git push -u origin master	Push local repo to remote repo in GitHub
$ git log	Shows commit logs
$ git help	Help manual
$ git pull	Pulls any changes from remote repo to local repo.

Step5: Create branch of existing repository in GitHub.

1.     Create a new dir and do $git init

2.     Clone a remote repo in local machine. Using Git clone command.                                           e.g. $ git clone 'https://github.com/danesm/GithubDemo.git'   

3.     Cd into new local repo

4.     Now create a new branch of master repo which you just cloned. By using following commands - git branch branchdemo1

5.     git checkout branchdemo1

6.     Now add a new file to the branch. By using – $ touch ‘newfile.html’

7.     Now you have a branch named ‘branchdemo1’of master repo ‘GithubDemo’ created on local machine. And have added a new file to the branch.

8.     At the moment the new file is not visible to master repo.

9.     Now do usual git add and commit operations on local branch repo to add the new file.

10.  Check everything is fine - $git status

11.  Checkout master and pull any new changes that might have been pushed by other users. $git checkout master and then $git pull

12.  Now go back to the local branch using- $git checkout branchdemo1

13.  Then merge with master using - $git merge master -m “comments”

14.  Then, $git push –set-upstream origin branchdemo1, this will push all latest changes from local branch to remote repo.

15.  Now go to GitHub page and refresh the repo to see the new branch. So now we can see the new branch but the file ‘branchdemofile.html’ is still not visible. This is because we need to first create pull request and then accept changes into master repo.

16.  Use $git branch command to check which branch you are in.

              

17.  Now go to the GitHub master repo page and create a pull request which will be reviewed by all owners and then accepted or rejected for further improvement.

       

                

18.  Now you can see all changes from the branch inside the master repo. And your changes are ready for other users of master repo to pull.

19.  Next step is to update your local master repo with your branch changes. So just switch to local master and perform a git pull to make sure you have all latest from remote master repo.

20.  Now after pull request is accepted, the new file is visible in master branch.

           

So now we have successfully created a new local branch of remote repo and added new file to the branch then pushed changes to remote repo using- pull request process.

Additional Info:

Following is log of the terminal to compare if you want to follow the steps.

Step6: Using SSH keys with GitHub

·      Connect to GitHub without supplying username and password every time you push code.

·      This will be specific to your laptop/computer

·      ls -al ~/.ssh to see if existing SSH keys are present

·      If you don’t want to use existing ones you can create new ones

·      Warning!! Always remove your SSH key if changing/selling computer.

·      Warning!! Do not use SSH login in public/shared computer.

 

      

 Create SSH keys :

·      $ ssh-keygen -t rsa -b 4096 -C "your_email@example.com"

·      This creates a new ssh key, using the provided email as a label.

·      Creates public/private rsa key pair.

·      Use default file names unless its required to change.

·      Now add keys to SSH agent and store password in keychain

$ ssh-add -K ~/.ssh/id_rsa

 Add the SSH public key to GitHub repo:

·      $ pbcopy < ~/.ssh/id_rsa.pub

·      Copies the contents of the id_rsa.pub file to your clipboard

·      Paste the key into your account’s settings > SSH Keys text box

·      $ git remote –v to view existing remotes.

·      To change the remote URL from HTTPS to SSH

·      $ git remote set-url origin git@github.com:USERNAME/REPOSITORY.git

      After this you no need to provide username or password for pushing the changes.

      If you work on a different repo , just add the keys using following and it will be all set.

      $ ssh-add -K ~/.ssh/id_rsa

       Thank you.