Clear Understanding About Version Control Systems through Git

Photo by Bitbucket

Git is an Open Source Distributed Version Control System. Now that’s a lot of words to define Git.

Let me break it down and explain the wording:

  • Control System: This basically means that Git is a content tracker. So Git can be used to store content — it is mostly used to store code due to the other features it provides.
  • Version Control System: The code which is stored in Git keeps changing as more code is added. Also, many developers can add code in parallel. So Version Control System helps in handling this by maintaining a history of what changes have happened. Also, Git provides features like branches and merges, which I will be covering later.
Version Control System
  • Distributed Version Control System: Git has a remote repository that is stored in a server and a local repository which is stored in the computer of each developer. This means that the code is not just stored in a central server, but the full copy of the code is present in all the developers’ computers. Git is a Distributed Version Control System since the code is present in every developer’s computer. I will explain the concept of remote and local repositories later in this blog.
Distributed Version Control System

Why a Version Control System like Git is needed

In real life projects generally have multiple developers working in parallel. So a version control system like Git is needed to ensure there are no code conflicts between the developers.

Additionally, the requirements in such projects change often. So a version control system allows developers to revert and go back to an older version of the code.

Finally, sometimes several projects which are being run in parallel involve the same codebase. In such a case, the concept of branching in Git is very important.

Let’s get started on using Git now

Rather than mentioning all the concepts at once, I will explain the concepts of Git through an example step by step. So that it is easier to follow.

Download git

This link has details on how to install Git in multiple operating systems:

Verify if Git is installed by using the following command in the command prompt:

Version Checking code

Now the git bash install in our system so let me open up a git bash and start using it. But before do anything we have to configure for the first time stating what would be the user name and the email id with which I want git bash to configure with. The command is:

User Name & Email Configure

Let us check if the configuration is set correctly:

Checking Configuration Details

Create your local Git repository

In your computer, create a folder for your project. Let’s call the project folder simple-git-demo.

Go into your project folder and add a local Git repository to the project using the following commands:

cd simple-git-demo
git init

The git init command adds a local Git repository to the project.

Let’s Add some Small Code now

Create a file called demo.txt in the project folder and add the following text into it:

Initial Content

Here we will be demoing with just plain text instead of actual code, since the main focus of this article is on Git and not on any specific programming language.

Staging and Committing the code

Committing is the process in which the code is added to the local repository. Before committing the code, it has to be in the staging area. The staging area is there to keep track of all the files which are to be committed.

Any file which is not added to the staging area will not be committed. This gives the developer control over which files need to be committed.

Staging

Use the following command for staging the file:

git add demo.txt

In case you want to add multiple files you can use:

git add file1 file2 file3

If you want to add all the files inside your project folder to the staging area, use the following command:

git add .

Use this carefully since it adds all the files and folders in your project to the staging area.

Committing

Use the following command to commit the file:

git commit -m "Initial Commit"

“Initial Commit” is the commit message here. Enter a relevant commit message to indicate what code changes were done in that particular commit.

Git Status and Git Log

Now modify the demo.txt file and add the following snippet:

Initial Content Adding more Content

Status

Use git status to find out information regarding what files are modified and what files are there in the staging area — it shows other information as well, which we can ignore for now.

Use the following command to see the status:

git status

The status shows that demo.txt is modified and is not yet in the staging area.

Now let us add demo.txt to the staging area and commit it using the following commands:

git add demo.txt git commit -m "demo.txt file is modified"

Log

Use git log to print out all the commits which have been done up until now.

The command used for this is:
git log

The log shows the author of each commit, the date of the commit, and the commit message.

Branches

Up until now, we have not created any branch in Git. By default, Git commits go into the master branch.

What is a branch?

A branch is nothing but a pointer to the latest commit in the Git repository. So currently our master branch is a pointer to the second commit “demo.txt file is modified”.

Why are multiple branches needed?

Multiple branches are needed to support multiple parallel developments. Refer to the image below to see how branches work.

Multiple Branch

Initially, commit 1 and commit 2 were done in the master branch. After commit 2 a new Branch called as “Test” is created, and commit 3 and commit 4 are added to the test branch.

At the same time, a different commit 3 and commit 4 are added to the master branch. Here we can see that after Commit 2, two parallel developments are being done in 2 separate branches.

The Test Branch and the Master Branch have diverged here and have different code — the code from Test Branch can be merged with the Master branch using git merge. This will be covered after a few topics.

Create a New Branch in Local

Create a new branch called test using the following command:

git branch test

This command creates the test branch.

We are still in the context of the master branch. In order to switch to the test branch. use the following command:

git checkout test

Now we are in the test branch.

You can list out all the branches in local using the following command:

git branch

Do Some Commits in the New Branch

Modify demo.txt by adding the following snippet:

Initial Content Adding more Content Adding some Content from test Branch

Now stage and commit using the following commands:

git add demo.txt git commit -m "Test Branch Commit"

This commit was done in the Test Branch, and now Test Branch is ahead of Master Branch by 1 commit — as the test branch also includes the 2 commits from the master branch.

You can verify the commit history in Test Branch using:

git log

Merging

Currently, Test Branch is ahead of the Master by 1 commit. Let’s say that now we want all the code in the Test Branch to be brought back to the Master Branch. This is where git merge is very useful.

In order to merge the code from the test branch into the master branch, follow these steps:

First, go back to the master branch:

git checkout master

Then run the merge command:

git merge test

After running these 2 commands, the merge should be successful. In this example, there are no conflicts.

But in real projects, there will be conflicts when a merge is being done. Resolving the conflict is something which comes with experience, so as you work more with Git you will be able to get the hang of resolving conflicts.

Run git log now and you will notice that the master also has 3 commits.

The Remote Git Repository

Until now, we have been working only in the local repository. Each developer will work in their local repository but eventually, they will push the code into a remote repository. Once the code is in the remote repository, other developers can see and modify that code.

GitHub

Here we will be using GitHub for the remote repository.

Go to https://github.com/ and create an account.

After registering on the GitHub homepage, click on Start a Project to create a new Git repository. Give the repository a name and click “Create Repository”

Give the name as git-blog-demo.

This will create a remote repository in GitHub, and when you open the repository, a page like an image below will open up:

The repository URL is the highlighted portion https://github.com/arunprashanth6/git-blog-demo.git

In order to point your local repository to the remote repository, use the following command:

git remote add origin [repository url]

Git Push

In order to push all the code from the local repository into the remote repository, use the following command:

git push -u origin master

This pushes the code from the master branch in the local repository to the master branch in the remote repository.

Additional Commands

Git Pull

git pull is used to pull the latest changes from the remote repository into the local repository. The remote repository code is updated continuously by various developers, hence git pull is necessary:

git pull origin master

Git Clone

git clone is used to clone an existing remote repository into your computer. The command for this is:

git clone [repository url]

Referance:

Software Engineer at Virtusa (Pvt) Ltd.