Introduction to Git and Github

CANDEV 2022

By Jason Jensen

Git vs Github

  • Git is a version control system
  • GitHub is an internet service used to centrally store git repositories

Why use Git?

Controlling versions can be difficult

Final.doc cominc
Source: PhD comics

With Git, one can

  • Track all changes made to a code base, with context
  • Revert changes at any time
  • Work on multiple copies of the code without endless folders
  • Have multiple people work on the same code without breaking things
  • More...

Git concepts

Modifying and committing code

All code lines exist in one of three states.

  • Modified: Code that has been changed and now differes from the latest committed copy, but is not yet staged.
  • Staged: Modified code must be added to the staging area to be committed. Only staged code gets committed.
  • Committed: Changes that are now committed to the code history. Usually alongside a commit message.

Modifying and committing code

Modified code stays in your local copy unless staged and committed.

Final.doc cominc
Source: Munira Omar

Branching and merging

  • All git repositories contain one or more branches.
  • Branches are independent copies of the same code base.
  • Branches share the same history prior to the branch point.
  • Branches will diverge over time unless merged.

Branching and merging

Git branching
Source: modified from Noble Desktop

Using github for your Candev submission

Step 1: create a GitHub account

Step 2: set up SSH

  • Create a local SSH key and add it to your agent
  • Add the key to your GitHub account

Click here for detailed guides on the GitHub website.

Step 3: Make a new github repo

Github new repo button2

Step 3: Make a new github repo

Github new repo button

Step 3: Make a new github repo

Github new repo button

Step 4: Setup your local git credentials

Open Git BASH (Windows) or terminal (mac/linux) and add your name and email:


git config --global user.name "Jason Jensen"
git config --global user.email jason.jensen@statcan.gc.ca

Note: email should match GitHub email.

Step 5: Copy the suggested code from your new repo

Github new repo button

Step 6: Do the initial commit

  1. Open Git BASH (windows) or terminal (mac/linux)
  2. Make a new folder:
    3. mkdir team-awesomes-CANDEV-project
  3. Change directory to the new folder:
    4. cd team-awesomes-CANDEV-project
  4. Paste and execute the code copied from github.

Errors may result if SSH was not configured correctly.

Step 7: Do the coding project

CANDEV brainstormning
Source: CANDEV 2018

Step 8: Copy your solution to the repository folder

Step 9: Add files to the staging area

Using Git BASH (windows) or terminal (mac/linux) in the repository folder:

  • List modified files:
    • git status
  • Add all modified files:
    • git add .

    Note: files can also be added one at a time.

    Note: use a .gitignore file to exclude groups of files/folders.

Step 10: Commit staged files

  • Confirm staged files:
    • git status
  • Commit staged files:
    • git commit -m "add submission files"
  • Push commit to GitHub:
    • git push origin main
  • Reload GitHub page to confirm files have been added.

Step 11: Include repo URL in CANDEV submission form

More details on the commit flow

Setup

Situation: repo is set up with a README.md file.

  • Add a line to the README.md file.
    • README.md contents
  • Make a file named "dont_commit_this.py".

Checking the status

  • See which files have changed:
    • git status
    git status output

Checking the diff

  • Investigate what has changed:
    • git diff README.md
    git diff output

Committing only some files

  • Commit the changed readme:
    • git add README.md
git status
    git diff output

Committing and pushing staged changes

  • Commit the changes
    • git commit -m "change readme"
    git commit output
  • Pushing the commit to github
    • git push origin main
    git push output

Ignoring files

Ignoring files

  • The untracked file is still showing up:
    • git status
    git status output

Ignoring files

  • This can be fixed with a .gitignore file

    • Note: no characters before the filetype extension (before the period)

  • The gitignore file takes various gulp-like patterns:
    • gitignore contents

Ignoring files

  • Check the status:
    • git status
    git status output

Example .gitignore files: https://github.com/github/gitignore

Back matter

Topics not covered

  • Branching and merging
  • Merging conflicts
  • GUI tools (Git GUI, VS Code, GitKraken, others)
  • Git hooks (automation)
  • GitHub/GitLab features (Issue reporting, github pages, CI/CD pipelines, etc.)
  • Probably other things too...

Other sources and inspirations

Jacob Fiksel: Introduction to Git and GitHub

Munira Omar: An Intro to Git and GitHub for Beginners Part I (Tutorial)