Github Primer

 

A Short History of Git

Github

Version control or source control is an important part of application development. 

It records every change made to files over time in case you need to revert to the previous file version.

The birth of the Git tools and the Github site came out of the need to keep track of code changes during the early days of linux development.

 Linus Torvalds started development on this project in the early 1990’s. By switching to a GPL (General Public License) he was able to attract developers for this massive project and code would be free for use.  Keeping track of all this code from various developers became unmanageable and a tool needed to handle this operation.

The first package to attempt to handle this massive task was called Bitkeeper. By 2002 it was clear that this package needed an overhaul and Git was created.

Linux became one of the largest software projects ever and consisted of millions of lines of code.

Some key concepts needed for a source code management system. 

Traceability, software bugs can be identified.  

A distributed Workflow so developers can have access to all the work on the project. 

Needed to be fast and safe from corruption.

Linus Torvalds quote "I'm an egotistical bastard, and I name all my projects after myself. First 'Linux', now 'git'." With Git being a British expression for a contemptible or silly person.

Linus Torvalds torvalds@linux-foundation.org

Reversibility: If you write code that breaks everything at 4:00 PM, you can instantly "rewind" the entire project back to how it looked at 9:00 AM.

Collaboration: It allows multiple people to work on the exact same files simultaneously without overwriting each other's work.

Accountability: It keeps a detailed log of who changed what, when, and why.

Experimentation: You can create a "Branch" (a sandbox copy) to try out a wild new feature. If it works, you merge it back; if it fails, you just delete the branch and the main project remains untouched.

Implementation and design of a Reliable,  High-performance, Distributed, Content Manager
Performance and distributed nature

Security and trust issues

Commit changes without disturbing others
Trust your data
Not a single point of failure

What is Git?

Git is a distributed version-control system for tracking changes in code

during software development. 

A GitHub repository is a storage space where your project's files are in one centralized location, allowing you to manage and share code with collaborators.

 

fast-version-control 

What is GitHub?

GitHub is a platform for version control and collaboration. It uses concepts like repositories, branches, commits, and Pull Requests. 

What is a Git repository?

 A Git repository is the .git/ folder inside a project.

Tracks all changes made to project files .

You can create a git repository from your local files or you can pull down a hosted repository from the github site.

Initializing a Repository in an Existing Directory

Project directory  and you want to start controlling it with Git, 

To create a repository on your local system you should create a directory to hold your files.

john_iacovacci1@cloudshell:~ (cloud-project-examples)$ mkdir python-invoicer

john_iacovacci1@cloudshell:~ (cloud-project-examples)$ cd python-invoicer

john_iacovacci1@cloudshell:~/python-invoicer (cloud-project-examples)$ 

john_iacovacci1@cloudshell:~/python-invoicer (cloud-project-examples)$ git init

Initialized empty Git repository in /home/john_iacovacci1/python-invoicer/.git/

john_iacovacci1@cloudshell:~/python-invoicer (cloud-project-examples)$ 

Git has 3 stages:

Untracked: file exists, not under git's version control.

Staged: file added to git control but changes not been committed.

Committed: the change has been committed.

Check the  state of the working directory and the staging area.

john_iacovacci1@cloudshell:~/python-invoicer (cloud-project-examples)$ git status

On branch master

No commits yet

nothing to commit (create/copy files and use "git add" to track)

john_iacovacci1@cloudshell:~/python-invoicer (cloud-project-examples)$ 

Create a README.md file

 

Markdown(.md) is a markup language with plain-text-formatting syntax,  

# python-invoicer project

This is a sample README.md file

Python invoicer will produce an invoice on products sold

john_iacovacci1@cloudshell:~/python-invoicer (cloud-project-examples)$ git status

On branch master

No commits yet

Untracked files:

  (use "git add <file>..." to include in what will be committed)

        README.md

nothing added to commit but untracked files present (use "git add" to track)

john_iacovacci1@cloudshell:~/python-invoicer (cloud-project-examples)$ 

 

Add README.md to  in the working directory to the staging 

john_iacovacci1@cloudshell:~/python-invoicer (cloud-project-examples)$ git add README.md

john_iacovacci1@cloudshell:~/python-invoicer (cloud-project-examples)$ git status

On branch master

No commits yet

Changes to be committed:

  (use "git rm --cached <file>..." to unstage)

        new file:   README.md

john_iacovacci1@cloudshell:~/python-invoicer (cloud-project-examples)$ 

Git commit is used to save your changes to the local repository

john_iacovacci1@cloudshell:~/python-invoicer (cloud-project-examples)$ git config --global user.email "john.iacovacci1@gmail.com" 

john_iacovacci1@cloudshell:~/python-invoicer (cloud-project-examples)$ git config --global user.name "Google Cloud Developer"

john_iacovacci1@cloudshell:~/python-invoicer (cloud-project-examples)$  git commit -m "First file in python-invoicer repository"

 

[master (root-commit) fbb6be2] First file in python-invoicer repository

 1 file changed, 3 insertions(+)

 create mode 100644 README.md

john_iacovacci1@cloudshell:~/python-invoicer (cloud-project-examples)$ 

john_iacovacci1@cloudshell:~/python-invoicer (cloud-project-examples)$ git status

On branch master

nothing to commit, working tree clean

john_iacovacci1@cloudshell:~/python-invoicer (cloud-project-examples)$ 

john_iacovacci1@cloudshell:~/python-invoicer (cloud-project-examples)$ ls -al

total 16

drwxrwxr-x  3 john_iacovacci1 john_iacovacci1 4096 Feb 18 18:05 .

drwxr-xr-x 79 john_iacovacci1 john_iacovacci1 4096 Feb 18 18:21 ..

drwxrwxr-x  8 john_iacovacci1 john_iacovacci1 4096 Feb 18 18:25 .git

-rw-r--r--  1 john_iacovacci1 john_iacovacci1  115 Feb 18 18:09 README.md

john_iacovacci1@cloudshell:~/python-invoicer (cloud-project-examples)$ 

 

Change into the .git directory to look at files (managed by git do not change)

john_iacovacci1@cloudshell:~/python-invoicer (cloud-project-examples)$ cd .git

Review the created git structure

john_iacovacci1@cloudshell:~/python-invoicer/.git (cloud-project-examples)$ ls -al

total 52

drwxrwxr-x 8 john_iacovacci1 john_iacovacci1 4096 Feb 18 18:25 .

drwxrwxr-x 3 john_iacovacci1 john_iacovacci1 4096 Feb 18 18:05 ..

drwxrwxr-x 2 john_iacovacci1 john_iacovacci1 4096 Feb 18 17:54 branches

-rw-rw-r-- 1 john_iacovacci1 john_iacovacci1   41 Feb 18 18:23 COMMIT_EDITMSG

-rw-rw-r-- 1 john_iacovacci1 john_iacovacci1   67 Feb 18 17:54 config

-rw-rw-r-- 1 john_iacovacci1 john_iacovacci1   73 Feb 18 17:54 description

-rw-rw-r-- 1 john_iacovacci1 john_iacovacci1   23 Feb 18 17:54 HEAD

drwxrwxr-x 2 john_iacovacci1 john_iacovacci1 4096 Feb 18 17:54 hooks

-rw-rw-r-- 1 john_iacovacci1 john_iacovacci1  137 Feb 18 18:23 index

drwxrwxr-x 2 john_iacovacci1 john_iacovacci1 4096 Feb 18 17:54 info

drwxrwxr-x 3 john_iacovacci1 john_iacovacci1 4096 Feb 18 18:23 logs

drwxrwxr-x 7 john_iacovacci1 john_iacovacci1 4096 Feb 18 18:23 objects

drwxrwxr-x 4 john_iacovacci1 john_iacovacci1 4096 Feb 18 17:54 refs

john_iacovacci1@cloudshell:~/python-invoicer/.git (cloud-project-examples)$ 

 

Check the repository using git log A Git log is a running record of commits.

john_iacovacci1@cloudshell:~/python-invoicer/.git (cloud-project-examples)$ cd ..

john_iacovacci1@cloudshell:~/python-invoicer (cloud-project-examples)$ git log

commit fbb6be239c112c9ac32a7fa5dcb16527d7d39ba3 (HEAD -> master)

Author: Google Cloud Developer <john.iacovacci1@gmail.com>

Date:   Wed Feb 18 18:23:57 2026 +0000

    First file in python-invoicer repository

john_iacovacci1@cloudshell:~/python-invoicer (cloud-project-examples)$ 

Now we can edit the README.md file by adding lines

Collects customer information

Display Inventory

Calculates Invoice based upon customer quantity

john_iacovacci1@cloudshell:~/python-invoicer (cloud-project-examples)$ git status

On branch master

Changes not staged for commit:

  (use "git add <file>..." to update what will be committed)

  (use "git restore <file>..." to discard changes in working directory)

        modified:   README.md

no changes added to commit (use "git add" and/or "git commit -a")

john_iacovacci1@cloudshell:~/python-invoicer (cloud-project-examples)$ 

 

Create account on github.com

I used continue with Google

 

 

Create new repository

 

 

 Create new repository called python-invoicer

 

 

 

 

 

 

 

Need to connect with github

Check for share ssh key with github

john_iacovacci1@cloudshell:~/python-invoicer (cloud-project-examples)$ ls -al ~/.ssh

 Generate key

john_iacovacci1@cloudshell:~/python-invoicer (cloud-project-examples)$ ssh-keygen -t ed25519 -C "john.iacovacci1@gmail.com"

Wake up keychain manager

john_iacovacci1@cloudshell:~/python-invoicer (cloud-project-examples)$ eval "$(ssh-agent -s)"

Hand key to manager

john_iacovacci1@cloudshell:~/python-invoicer (cloud-project-examples)$ ssh-add ~/.ssh/id_ed25519

Make key visible to copy to github

john_iacovacci1@cloudshell:~/python-invoicer (cloud-project-examples)$ cat ~/.ssh/id_ed25519.pub

Put ssh key in gitbub - Settings

Deploy keys

Paste key values

You can now connect to github

john_iacovacci1@cloudshell:~/python-invoicer (cloud-project-examples)$ git remote add origin https://github.com/jiacovacci/python-invoicer.git

Push committed code up to site

john_iacovacci1@cloudshell:~/python-invoicer (cloud-project-examples)$ git push -u origin main

README.md file now on github

 

 

 

Put the invoicer program form homework assignment in directory

Add files to repository

john_iacovacci1@cloudshell:~/python-invoicer (cloud-project-examples)$ git add invoicer.py

john_iacovacci1@cloudshell:~/python-invoicer (cloud-project-examples)$ git commit -m "Invoicer"

[main c11bb1c] Invoicer

 2 files changed, 140 insertions(+)

 create mode 100644 invoicer.py

john_iacovacci1@cloudshell:~/python-invoicer (cloud-project-examples)$ git push -u origin main

Enumerating objects: 6, done.

Counting objects: 100% (6/6), done.

Delta compression using up to 4 threads

Compressing objects: 100% (4/4), done.

Writing objects: 100% (4/4), 1.12 KiB | 573.00 KiB/s, done.

Total 4 (delta 0), reused 0 (delta 0), pack-reused 0

To github.com:jiacovacci/python-invoicer.git

   fbb6be2..c11bb1c  main -> main

branch 'main' set up to track 'origin/main'.

john_iacovacci1@cloudshell:~/python-invoicer (cloud-project-examples)$