index

Version Control with Git

0. Introduction

Before We Start

Create an account at github.com
Open up a terminal

1. What is Version Control?

What Does It Do?

Tracks changes to files
Any file can be tracked
Text (.txt, .csv, .py, .c, .R, etc.) works best
- These allow smart diff / merge etc.

Why Use Version Control?

A more efficient backup
Reproducibility

Why Use Version Control?

Teamwork

Version Control Tracks Changes

Changes are tracked sequentially

Version Control Tracks Changes

Different versions can be saved

Version Control Tracks Changes

Multiple versions can be merged

Version Control Alternatives

Git
- Distributed
Subversion (svn)
- Centralised
Mercurial (hg)
- Distributed
Git most widely used in academia
- GitHub
- GitLab

Graphical Version Control

Sourcetree	Git Kraken	Git Desktop

GUIs

PyCharm	RStudio	VS Code

2. Setting Up Git

Key Commands

git config --global user.name "Your Name"
git config --global user.email "yourname@gmail.com"
git config --global core.editor "nano -w"

Setting Up GitHub

Sign up to GitHub: https://github.com/signup
Open a terminal
ssh-keygen -t ed25519
Yes to everything
cat ~/.ssh/id_ed25519.pub
Copy the contents to GitHub: https://github.com/settings/ssh/new

3. Creating a Repository

GitHub Template

Go to https://github.com/Southampton-RSG-Training/git-novice-template
“Use This Template”
Name it climate-analysis

Key Commands

git clone git@github.com:yourname/climate-analysis
cd climate-analysis
ls -a
git status

4. Tracking Changes

Key Commands

nano README.md
git add README.md
git status
git commit -m "Your message"

Adding & Committing

Repository structure

Key Commands

git status
git log
nano climate_analysis.py
git diff
git add climate_analysis.py
git commit -m "Your message"

Challenge

Use nano to edit climate_analysis.py
Add “# TODO: Add rainfall processing code” to the end
Commit the change to the repository

Solution

nano climate_analysis.py
git diff
git add climate_analysis.py
git commit -m "Your message"

5. Exploring History

Key Commands

git log
git diff HEAD~1 climate_analysis.py
git diff HEAD~2 climate_analysis.py

Challenge

Get the ID of your first commit
Get a summary of the changes to climate_analysis.py since then

Solution

git log
Take the first 7 characters of the last commit
git diff <COMMIT ID> climate_analysis.py

More Differences

Differences of specific commits

Key Commands

rm climate_analysis.py
git status
git restore climate_analysis.py

Advanced Use

git checkout <COMMIT ID> climate_analysis.py

Restoring Files

Restore files to specific commits

6. Remote Repositories

Local Repo

Remote Backups

Collaboration

Collaboration via remote repository

Key Commands

git push

Conflict Creation

Local:

nano README.md
Add your email to the end
git commit -am "Your message"

Remote:

Go to your repo on GitHub
Edit README.md to add install info to the end
Commit directly to main

Conflict Resolution

git pull
git config pull.rebase false if it fails
nano README.md and remove the <<</===/>>>
git commit -am "Your message"
git push

Remote Commands

7. Branches

Feature-branch

Branching off a master branch

Creating branches

git branch
git branch dev
git switch dev

Branch files

nano rainfall_conversion.py
git add rainfall_conversion.py
git commit -m "Your message"
ls
git log

Switching Branches

git switch main
ls
git log

Pushing Branches

git switch dev
git push origin dev
git config --global push.autoSetupRemote true

Merging Branches

git switch main
git merge dev

8. Ignoring Things

Create Temporary Files

git switch dev
mkdir results
touch a.dat b.dat results/a.out results/b.out
git status

Create Git Ignore

nano .gitignore
Lines for *.dat and results/
git status
git add .gitignore
git commit -m "Your message"