Git Basics

Jeronimo Rodriguez-Escobar 2023-02-28

Git

NOTE. This is an ongoing document, it is not complete and can be improved, but it already has some basic instructions.

Git is a distributed version control system. This document has a great introduction on Version control.

Git was originally developed to to help groups of developers work collaboratively on big software projects.

Its purpose is to manage the evolution of a group of files (known as repo). (Track changes on steroids)

In Data Science, it is used to manage all the files associatd with a data management project in a more structured manner:

Keeps all files together
Keeps track of all changes and allows to go back in time
Useful to keep updated versions among multiple machines/users
Facilitates teamwork and publishing

This video explains in very basic terms what git is about and the basic operations:

git init
git status
git commit
git branch
git push
git pull
git fetch

Installation.

Find instructions to install Git here, in case it is not installed in your computer yet. Check if Git is installed with this command:

$ git --version

Git can be used directly on the command line or trough GUIs. RStudio offers a very very intuitive approach. Instructions for setting it up are here

Seting the user

$ git config --global user.name "Jeronimo Rodriguez"
$ git config --global user.email jeronimo.rodriguez@temple.edu

Check Settings

$ git config --list

Setting the editor

I set EMACS as the default editor, it is not the only option, but the one I am familiar with

$ git config --global core.editor emacs

Starting a new repository

$ git init

Check the Git Status

$ git status

Git Commit

$ git commit

Create new branch

$ git checkout -b master

$ git branch
# Connecting to GitHub

Shift between branches

(from current to test1)

$ git checkout test1

GitHub

It is very common to threat Git and Github indistinctly as the same thing, it is important to consider their relartionship:
GitHub complements Git by providing a user interface and a distribution mechanism for Git repositories

Git is the software that records changes to a set of files.
GitHub is a hosting service that provides a Git-aware home for such projects on the internet. (Bryan, 2017)

Connecting with the Remote GitHub Repository

This link has the instructions to set the log in credential from your machines. It depends on the OS. It can be confusing at the beginning (it was and still is for me), because there are several ways to set it up (token, ssh, 2fA, password) and it is easy to forget. Insdtead of creating new instructions, just follow the instuctions. If you still experiment issues, contact me.

Adding locally created repositories to GitHub

In my opinion, the most common and intuitive way to start working in GitHub is by creating a repositoty on the website. However, it might be better to create if from the R project and then adding a remote repository In this operation, what happens is that the new repository, created together with the new proyect will be stored in the GitHub server. This has three main purposes:

Get a backup for you code outside your local machine
Track changes and the evolution of the software and workflows you are developing
Synchronize between multiple workstations and users

These are the main strengths of the Distributed Version Control Systems (DVCS) ## Create a new repository on the GitHub website

2 Go tho the Terminal tab, next to Console in your RStudio GUI

$ git remote add origin https://github.com/USER/REPO.git
# Change /USER/REPO for your user and the name of the repository on GitHub 
$ git remote -v
# Verify new remote
> origin  https://github.com/USER/REPO.git (fetch)
> origin  https://github.com/USER/REPO.git (push)

Depending on the method set to authenticate, the console might ask to the credentials Once the repository is created and synchronized on ghithub, you can clone it in other machines, set privacy or invite others to cooperate.

Tho add a local repository and start thracking:

# Check git status
git status
# add (stash) changes. Add each filename separated by coma
git add script1.R, script2.R .....
# to add all files:
git add --a
# commit changes
git commit # don't forget to add comment. Else the commit will not occur. Make sure to include meaningful comments here, this is key to be track, check advances.
# Set remote repository url (in case you have not done so)
$ git remote add origin https://github.com/USER/REPO.git
# Set remote repository as origin (this only needs to be done once) and push to remote
$ git push --set-upstream origin master

GitHub and RStudio

The basic git operations can be easilty run directly from RStudio. There is a nice intergration between them. The basics can be found here.

Cumaribo/tutorials