• Tracking and managing changes:

• Work faster and more reliably

• Keeps track of all code modifications:

• Specialised Database (Repository)

• Solves Common Team Problems:

• Conflicitng concurrent work,

• incompatiables due to concurrent working,

• having unstable releases

Historical information​ : Looking at the history of changes it is a lot easier to find where bugs have originated. Also, it might be easier to find the right team member best suited to fix an error.​

Branching​: Working concurrently on multiple issues, without interference.​ Working on different types of releases.​

Merging​ : Making sure that team members work does not interfere with each other.​

Traceability​ : Team members work more fluently together.​

Testing and Documentation​: Comments for each change and its association help producing better documentation​. Creating tests is easier​.

• Local:

  • Creates a database on the your hardware ​

• Centralised​:

  • History of changes kept in a single database in a central server.​
  • Clients need to constantly communicate with the database and receive a partial working copy.​

• Distributed​:

  • Single database in a central server that is also distributed among all clients​
  • Each client has a full working copy of the repository​

Local Data Model

• Revision Control System (RCS) [OS]
• Source Code Control System (SCCS) [OS]
• The Librarian [P]
• Panvalet [P]

Client Server model

• Concurrent Versions System [OS]
• Subversion (SVN) [OS]
• Vesta [OS]
• AccuRev [P]
• Autodesk Vault [P]
• CADES [P]
• ...
• Vault [P]
• Visual Source Safe [P]

• Developed by Linus Torvalds (you know the inventor/creator of Linux) to manage the development of Linux

• Over 76k commits to date (2025)

• First ever commit - e83c5163316f89bfbde7d9ab23ca2e25604af290 (21 years ago)

• Commit message: Initial revision of "git", the information manager from hell

                  GIT - the stupid content tracker

"git" can mean anything, depending on your mood.

- random three-letter combination that is pronounceable, and not
  actually used by any common UNIX command.  The fact that it is a
  mispronounciation of "get" may or may not be relevant.
- stupid. contemptible and despicable. simple. Take your pick from the
  dictionary of slang.
- "global information tracker": you're in a good mood, and it actually
  works for you. Angels sing, and a light suddenly fills the room. 
- "goddamn idiotic truckload of sh*t": when it breaks

...

• A very popular VCS
• Performance
• Better performance compared to competitors
• Deals with the data in the file rather than the file properties
• Security
• Designed to provide security
• Uses SHA-256 encryption
• Flexibility
• Non-linear development
• Detailed log of information

All commands are prepended with git

• init initialise a folder as a git repository

• fetch, pull: Get a working copy of a repository

• add,commit,push: Record a change or changes in at least one of the files stored in the repository.

• branch: Create a copy of a repository to be worked independently.

• merge: Collates changes of two different copies of a repository.

• log: Records information of each change within a repository

.git/
├── objects/               # Git's object database
│   ├── pack/              # Compressed repository data
│   └── info/              # Additional object information
│   └── [sha1]/            # Object storage using hash prefixes
├── refs/                  # Reference storage
│   ├── heads/             # Branch references
│   ├── tags/              # Tag references
│   └── remotes/           # Remote repository references
├── HEAD                   # Points to current branch
├── config                 # Repository configuration
├── index                  # Staging area information
├── hooks/                 # Scripts for automation
│   ├── pre-commit         # Run before commit is created
│   └── post-commit        # Run after commit is created
├── info/                  # Repository information
│   └── exclude            # Local ignore patterns
└── logs/                  # Reference history
    ├── HEAD               # History of HEAD updates
    └── refs/              # Branch update history

• As part of the version control features there is the Staging Area. ​

• This is feature enables the developer to move files independently of each other to the repository.

git add <filename>

git add .

git commit 

git commit -a

git commit -m

git commit -am

• Comparing hashes to see differences git diff <a_hash> <another_hash>

git diff 43ba0aa4935549d2d4245bedf455bbc25a5d1636 a1b2c3d4e5f67890abcdef1234567890abcdef12

sha1sum.exe <<< hello
f572d396fae9206628714fb2ce00f72e94f2258f *-

sha1sum.exe <<< Hello
1d229271928d3f9e2bb0375bd6ce5db6c6d348d9 *-

Example

GitHub - What is it and features?

Account creation

$ ssh-keygen -t ed25519 -C "s.blair@gre.ac.uk"
Generating public/private ed25519 key pair.
Enter file in which to save the key (/home/user/.ssh/id_ed25519): 
Enter passphrase (empty for no passphrase): 
Enter same passphrase again: 
Your identification has been saved in /home/user/.ssh/id_ed25519
Your public key has been saved in /home/user/.ssh/id_ed25519.pub
The key fingerprint is:
SHA256:Ue/4v8XYf6tK8DZ1zN8KHZl1k+GJZNmjqTz3KbR1nCo s.blair@gre.ac.uk
The key's randomart image is:
+--[ED25519 256]--+
|       .+.o=.    |
|      + B.Eo     |
|     o B.+       |
|    . + X        |
|     o S o       |
|      = .        |
|     . .         |
|      .          |
|                 |
+----[SHA256]-----+

Syncing Git and GitHub