• How to push and pull changes to and from remote repositories
• Using .gitignore to avoid tracking certain files
• Creating and managing branches with git branch and git checkout
• The difference between clone and fork repositories
• Resolving conflicts when multiple people change the same code
• Going back to specific commits with git checkout and git reset
• Workflow for merging branches back to master/main

Today we will cover:

• Understanding changes with git diff
• Amending commits with git commit --amend
• Cherry-picking commits with, well, git cherry-pick 😅
• Understanding git rebase and its uses
• Saving work temporarily with git stash
• Installing and setting up GitHub CLI
• GitHub CLI repository management
• Mock-up quiz!

• git diff shows you what has changed between commits, branches, or your working directory
• It is one of the most useful Git commands for understanding your code changes
• Helps you review changes before committing
• Let’s see how it works with our former my-project repository
• First, let’s make some changes in the 01-data-cleaning.py file

echo "# This is a data cleaning script" >> ./01-data-cleaning.py
git diff

• diff --git a/file b/file shows Git is comparing two versions of the same file (a = original, b = modified)
• --- a/file and +++ b/file indicate the original file (before) and new file (after) being compared
• @@ -0,0 +1 @@ shows the line numbers affected, with + lines indicating additions and - lines indicating deletions. -0,0 means that the original file had no lines, and +1 means one line was added

Basic diff commands:

• git diff: shows unstaged changes in working directory
• git diff --staged: shows staged changes ready to commit
• git diff HEAD: shows all changes since last commit
• git diff --name-only: shows only filenames that changed

Comparing commits:

• git diff commit1..commit2: compares two specific commits
• git diff branch1..branch2: compares two branches
• git diff --stat: shows summary of changes (files modified, insertions, deletions)

• @@ -1,4 +1,4 @@ means that in the original file, lines 1 to 4 were present, and in the new file, lines 1 to 4 are also present, but with some changes

Amending the commit message:

git commit --amend -m "New commit message"

Adding forgotten files:

git add forgotten-file.txt
git commit --amend --no-edit

Both together:

git add new-file.txt
git commit --amend -m "Updated commit message"

Important rules:

• Only amend local commits
• Never amend commits that have been pushed to a shared repository
• If you need to modify pushed commits, use git revert instead
• Always communicate with your team before amending shared history

• If you made a mistake, git allows you to undo commits
• git reset can move the HEAD pointer to a previous commit
• --soft keeps changes in the staging area
• --hard discards all changes after the specified commit
• Use with caution too! Hard reset will delete uncommitted changes

• git cherry-pick allows you to pick specific commits from one branch and apply them to another
• Useful when you want to apply a bug fix or feature from one branch to another
• Each commit is applied individually with its own commit message
• Can be used to backport changes to older versions
• Creates new commits rather than modifying existing ones

Basic cherry-pick:

# Cherry-pick a single commit
git cherry-pick abc1234

# Cherry-pick multiple commits
git cherry-pick abc1234 def5678

# Cherry-pick a range of commits
git cherry-pick abc1234..def5678

After cherry-picking:

• The commit is applied to your current branch
• It creates a new commit with the same changes
• Original commit history is preserved

Handling conflicts:

# If conflicts occur during cherry-pick
git cherry-pick --continue  # After resolving conflicts
git cherry-pick --abort     # Cancel the cherry-pick
git cherry-pick --skip      # Skip the current commit

Common use cases:

• Applying hotfixes to multiple branches
• Backporting features to release branches
• Moving specific commits between branches

• git rebase allows you to move or combine commits to a new base commit
• Changes the commit history by replaying commits on top of another base
• Creates a linear, clean commit history
• Useful for keeping feature branches up to date with main branch
• Rewrites commit history - avoid using it on shared or public branches!

Interactive rebase:

# Interactive rebase of last 3 commits
git rebase -i HEAD~3

# Interactive rebase to specific commit
git rebase -i abc1234

Rebase onto another branch:

# Rebase current branch onto main
git rebase main

# Rebase feature branch onto main
git checkout feature-branch
git rebase main

During interactive rebase you can:

• pick: use the commit as-is
• reword: change the commit message
• edit: modify the commit contents
• squash: combine with previous commit
• drop: remove the commit entirely
• reorder: change commit order

• git stash temporarily saves your uncommitted changes without committing them
• Think of it as a “clipboard” for your work-in-progress
• Useful when you need to switch branches but aren’t ready to commit
• Keeps your working directory clean without losing work
• Stashes are stored in a stack (last in, first out)

When to use git stash:

• You need to switch branches urgently (e.g., hotfix)
• You want to pull changes but have local modifications
• You’re experimenting and want to save your current state
• You accidentally started work on the wrong branch

Saving and restoring stashes:

# Stash current changes (tracked files only)
git stash

# Stash with a descriptive message
git stash save "WIP: adding user authentication"

# Stash including untracked files
git stash -u

# Stash including untracked and ignored files
git stash -a

# Restore most recent stash and remove from stack
git stash pop

# Restore most recent stash but keep in stack
git stash apply

Managing multiple stashes:

# List all stashes
git stash list

# Apply a specific stash
git stash apply stash@{2}

# Drop a specific stash
git stash drop stash@{1}

# Clear all stashes (use with caution!)
git stash clear

# Show changes in most recent stash
git stash show

# Show changes in stash with diff
git stash show -p stash@{0}

A very common scenario:

You’ve been coding away, only to realise you’re on the wrong branch! 😱

git stash makes it easy to move your uncommitted changes to the correct branch:

# You're on main but should be on feature-x
# First, stash your changes
git stash save "Move to feature-x branch"

# Switch to the correct branch
git checkout feature-x

# Apply your stashed changes
git stash pop

This technique works for both tracked and untracked files (use git stash -u for untracked).

Creating a new branch from stash:

If the branch doesn’t exist yet, you can create it directly from the stash:

# Stash your current work
git stash

# Create new branch with stashed changes
git stash branch new-feature-branch

This command:

• Creates a new branch from where you stashed
• Checks out the new branch
• Applies the stash
• Drops the stash if applied successfully

Pro tip: This is the safest way to recover stashed work if you’re unsure about conflicts!

• GitHub CLI (gh) is the official command-line tool for GitHub
• Allows you to work with GitHub directly from your terminal
• No need to open a web browser for common tasks
• Works seamlessly with Git workflows
• Supports authentication and works with your GitHub account

WSL/Ubuntu:

# Install
(type -p wget >/dev/null || (sudo apt update && sudo apt install wget -y)) \
    && sudo mkdir -p -m 755 /etc/apt/keyrings \
    && out=$(mktemp) && wget -nv -O$out https://cli.github.com/packages/githubcli-archive-keyring.gpg \
    && cat $out | sudo tee /etc/apt/keyrings/githubcli-archive-keyring.gpg > /dev/null \
    && sudo chmod go+r /etc/apt/keyrings/githubcli-archive-keyring.gpg \
    && sudo mkdir -p -m 755 /etc/apt/sources.list.d \
    && echo "deb [arch=$(dpkg --print-architecture) signed-by=/etc/apt/keyrings/githubcli-archive-keyring.gpg] https://cli.github.com/packages stable main" | sudo tee /etc/apt/sources.list.d/github-cli.list > /dev/null \
    && sudo apt update \
    && sudo apt install gh -y

# Update (if already installed)
sudo apt update && sudo apt install gh -y

macOS (using Homebrew):

# /bin/bash -c "$(curl -fsSL https://raw.githubusercontent.com/Homebrew/install/HEAD/install.sh)"
brew install gh

Verify installation:

gh --version

Repository operations:

# List your repositories
gh repo list

# Clone a repository
gh repo clone username/repo-name

# Create a new repository
gh repo create 

# View repository details
gh repo view --web

# Fork a repository
gh repo fork

# Star/unstar a repository
gh repo star

# Archive/unarchive a repository
gh repo archive

Pull requests and issues:

# Create a new pull request
gh pr create --title "My PR" --body "Description of my PR"

# List pull requests
gh pr list

# View pull request details
gh pr view 123 --web

# Create a new issue
gh issue create --title "My Issue" --body "Description of my issue"

# List issues
gh issue list

# View issue details
gh issue view 456 --web