Introduction to Git

plus GitHub, R & RStudio

OJ Watson

2025-01-21

Introduction to Git

• Git is a version control software (VCS).
• VCS: Takes a picture of what your files look like and stores that in memory.
• This allows us to look back and see how our files have changed over time.

Why do we need version control?

Version control: metadata + history

• who: name of person making changes
• when: date and time change
• what: contents of files changed
• why: motivation for the change

Is it just like a backup?

• Why not just use Dropbox?

• Or Google Drive?

• These are also great to use, and Google docs for example has version control where changes are tracked.

• However, Git and Github are made specifically for tracking how codebases have changed.

Installing Git

Git supports all operating systems. You can install it using command-line tools or directly download and install the setup.

https://git-scm.com/book/en/v2/Getting-Started-Installing-Git

• Linux

  • For Debian/Ubuntu-based operating systems use apt-get install git or similar.

• macOS

  • If you have homebrew installed, use this command to download and install Git: brew install git.

• Windows

  • Installing Git on Windows is hassle-free. Just go to the download page

How to check if you have installed Git?

Open a terminal, type git --version and press enter

Link Git to your Github

git config --global user.name "your-user-name"
git config --global user.email "your@email.com"

Basic git terms

• repository: (or “repo”) git’s database. Might be local or on GitHub
• working copy: all the files you actually work with
• commit:
  • as a noun: a snapshot of all the files in the repository
  • as a verb: create a snapshot
• hash: fingerprint of a file/repository

Git history

Interacting with Git

• From the command line - always good to be comfortable with this
• From a GUI
  • RStudio has one built-in
  • Most IDEs do now (e.g. VSCode or Positron)
• Via GitHub

Basic git commands

• git init: initialise a repository
• git add: stage files
• git commit: add staged files to the repository by making a commit
• git log: see an overview of what changed
• git diff: see details of what changed

End of part 1

What makes a commit?

Ideally

• One set of related changes
• Commit message explains why they were needed
• Short title (<60 characters)
• Blank line, then any further discussion

Not everything goes in git

• Large files
• Passwords
• Outputs (sometimes)
• Use .gitignore

Remote git commands

• git clone: download a repository
• git fetch: update remote changes but don’t apply them
• git pull: update remote changes and do apply them
• git push: send your changes upstream
• git remote: inspect / change details of upstream repositories
• git branch: inspect / create a branch
• git checkout -b: create a branch and change to it (yes this is stupid)
• git merge: merge branches

Rstudio and GitHub

• Not all commands are supported but all you will likely need
• Use the shell for the rest