Git And Github
March 2023
Version control with Git
Git is a distributed version control system that allows developers to keep track of changes made to code over time. It was created by Linus Torvalds in 2005 to manage the development of the Linux kernel.
With Git, developers can create a repository to store their code and all of its versions. They can make changes to the code and commit those changes to the repository, creating a new version. Git keeps track of all of these versions, so developers can easily go back in time to see what changes were made and when.
Git uses a system of branches to allow developers to work on different versions of the code at the same time. Developers can create a new branch to work on a specific feature or bug fix, and then merge that branch back into the main code when they are finished.
Getting Started
Step 1: Install Git
First, you need to install Git on your computer. Go to the Git website and download the version that is appropriate for your operating system. Alternatively, if you use Anaconda, you can install Git by simply running conda install git.
Step 2: Set up Git
Once you have installed Git, you need to set up your user name and email address. Open the command line interface or terminal and enter the following commands:
git config --global user.name "Your Name"
git config --global user.email "your.email@example.com"
These commands will set your user name and email address, which will be associated with all of your Git commits.
Step 3: Create a Git repository
A Git repository is a folder that contains all of your project files and their version history. Create a new directory called myproject and initialize a new Git repository:
mkdir myproject
cd myproject
git init
Question: Where is the “repository” located? What’s changed?
Step 4: Add files to the repository
Create a plain text file hello.txt containing the following:
Hello Wolrd!
The file contains a typo that we will fix later.
Create a second file hola.txt containing the following:
hola mundo
Now that we have some files to work with, pick the files for which you want to track changes. Start by adding hello.txt:
git add hello.txt
Now type git status. Question: What do you see?
Next, add hola.txt:
git add hola.txt
You can also add both files in one command:
git add hello.txt hola.txt
…or add all the files in the current directory:
git add .
Step 5: Commit changes
You can now commit the changes for the files you selected. A commit is a core concept in git. It acts like a snapshot of the changes that you have made to the repository. To commit your changes, enter the following command:
git commit -m "My first commit"
Type git log. Question: What do you see?
Question: What happens if you don’t provide a message with -m?
Step 6: Make some changes
Open hello.txt and fix the typo:
Hello World!
Exit to the command line and type git status. Question: What do you see?
To commit the new changes you just made, repeat Step 4 & 5:
git add hello.txt
git commit -m "Fix typo"
Verify with git status and git log.
Step 7: Create a branch
You can think of a branch as a separate copy of your directory that you can work on without affecting the main branch.
We will create a new branch in which we will do work to make hola.txt a bit more fancy. To create a new branch, enter the following command:
git branch fancy-hola
Step 8: Switch to a branch
To switch to the new branch:
git checkout fancy-hola
Note: You can’t switch branches if your repository has “unsaved” changes. Either commit, stash, or undo your changes.
Step 9: Do some work in new branch
Edit hola.txt to be:
Hola Mundo
Save and commit:
git add hola.txt
git ci -m "Capitalize words"
Edit hola.txt again:
Hola Mundo!
Again, save and commit:
git add hola.txt
git ci -m "Add exclamation mark!"
Now check git log
Step 8: Merge branches
To merge changes from one branch into another, first switch to the branch you want to merge changes into.
Switch to the original branch (master/main):
git checkout master
git log
You can check with git log that your last two commits are not here!
Question: Open hola.txt. Are the changes there?
Now, to merge the changes from the other branch fancy-hola:
git merge fancy-hola
Check git log and hola.txt again to verify that the changes were applied.
Git tools
If the command line interface is inconvenient, there exist tools that make the experience much more graphic such as gitk and Git Kraken.