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Git Basics

What is Version Control System?

Version Control System (VCS) is a software that helps software developers to work together and maintain a complete history of their work.

Following are the types of VCS:

1. Centralized version control system (CVCS):
   • Store all files and enables team collaboration.
   • Drawback of CVCS is its single point of failure.
   • Disk of the central server gets corrupted and proper backup has not been taken, then you will lose the entire history of the project.
2. Distributed/Decentralized version control system (DVCS):
   • Latest snapshot of the directory but they also fully mirror the repository.
   • You can commit changes, create branches, view logs, and perform other operations when you are offline.

What is Git & It's Advantages?

• Free and open source
• Fast and Small
• Implicit Backup
• Security
• Easier branching

Git Objects

What is Blob?

• BLOB stands for Binary Large Object.
• Each version of a file in Git is represented as a BLOB. A BLOB holds a file’s data but doesn’t contain any metadata about the file or even its name.
• Example:

  • Created new directory called practice.

    abhishek@sf-cpu-438:~/Desktop$ mkdir practice
    abhishek@sf-cpu-438:~/Desktop$ cd practice
    

  • Initialized practice.

    abhishek@sf-cpu-438:~/Desktop/practice$ git init
    Initialized empty Git repository in /home/abhishek/Desktop/practice/.git/
    

  • Remove hooks and see tree.

    abhishek@sf-cpu-438:~/Desktop/practice$ rm -rf .git/hooks
    abhishek@sf-cpu-438:~/Desktop/practice$ rm -rf .git/hooks
    

    Output:

    .git
    |-- HEAD
    |-- branches
    |-- config
    |-- description
    |-- info
    |   `-- exclude
    |-- objects
    |   |-- info
    |   `-- pack
    `-- refs
        |-- heads
        `-- tags
    
    8 directories, 4 files
    

  • Created three files: file1 - Hello, file2 - Hello and file3 - Hello World

  • Add to stage area. Whenever we are adding to stage area then blobs are created for each n every distinct file.

    abhishek@sf-cpu-438:~/Desktop/practice$ touch file1
    abhishek@sf-cpu-438:~/Desktop/practice$ touch file2
    abhishek@sf-cpu-438:~/Desktop/practice$ touch file3
    abhishek@sf-cpu-438:~/Desktop/practice$ git add .
    abhishek@sf-cpu-438:~/Desktop/practice$ tree .git
    

    Output:

    abhishek@sf-cpu-438:~/Desktop/practice$ cd .git
    abhishek@sf-cpu-438:~/Desktop/practice/.git$ cd objects
    abhishek@sf-cpu-438:~/Desktop/practice/.git/objects$ ls
    55  e9  info  pack
    

  • Add two empty file. It will add blobs for empty file also.

    abhishek@sf-cpu-438:~/Desktop/practice$ touch file4
    abhishek@sf-cpu-438:~/Desktop/practice$ touch file5
    abhishek@sf-cpu-438:~/Desktop/practice$ git add .
    abhishek@sf-cpu-438:~/Desktop/practice$ tree .git
    

    Output:

    .git
    |-- HEAD
    |-- branches
    |-- config
    |-- description
    |-- index
    |-- info
    |   `-- exclude
    |-- objects
    |   |-- 55
    |   |   `-- 7db03de997c86a4a028e1ebd3a1ceb225be238
    |   |-- e6
    |   |   `-- 9de29bb2d1d6434b8b29ae775ad8c2e48c5391
    |   |-- e9
    |   |   `-- 65047ad7c57865823c7d992b1d046ea66edf78
    |   |-- info
    |   `-- pack
    `-- refs
        |-- heads
        `-- tags
    
    11 directories, 8 files