Git Guide: From Junior to Expert

Git_Guide.md

🚀 Git Guide

A progressive guide to master Git, from your first commits to advanced techniques

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📋 Table of Contents

• 🟢 Beginner Level
• 🟡 Intermediate Level
• 🔵 Advanced Level
• 🔴 Expert Level

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🟢 Beginner Level

Initial Configuration

git config - Git Configuration

Usage: Defines your identity and Git preferences

# Global configuration
git config --global user.name "DorianABDS"
git config --global user.email "[email protected]"

# Check configuration
git config --list
git config --global --list

💡 Tip: This step is crucial for identifying your contributions!

Initialization and Cloning

git init - Create a new repository

Usage: Initializes a Git repository in an existing folder

mkdir my-project
cd my-project
git init

✅ Result: Creates a hidden .git folder containing the history

git clone - Copy an existing repository

Usage: Clones a remote repository to your machine

# Clone via HTTPS
git clone https://github.com/user/project.git

# Clone with custom name
git clone https://github.com/user/project.git my-project

# Clone a specific branch
git clone -b develop https://github.com/user/project.git

Staging Cycle

git add - Prepare files

Usage: Adds modifications to the index (staging area)

# Add a specific file
git add index.html

# Add all modified files
git add .

# Add all files of a type
git add *.js

# Add interactively
git add -p

📊 File states: Untracked → Staged → Committed

git commit - Record modifications

Usage: Creates a snapshot of your modifications with a descriptive message

# Commit with message
git commit -m "feat: add login page"

# Add + commit in one command (already tracked files)
git commit -am "fix: fix display bug"

# Modify the last commit
git commit --amend -m "New message"
git commit --amend --no-edit  # Keep the message

🎯 Convention: Use clear and conventional messages!

Tracking and Inspection

git status - Repository state

Usage: Shows the current state of your working directory

git status

# Short version
git status -s

Symbol legend:

• ?? = Untracked
• A = Added (new file)
• M = Modified
• D = Deleted

git log - Commit history

Usage: Explores the modification history

# Complete history
git log

# One line per commit
git log --oneline

# With branch graph
git log --graph --oneline --all

# Last commits
git log -5

# By author
git log --author="DorianABDS"

# Between two dates
git log --since="2024-01-01" --until="2024-12-31"

git diff - Compare modifications

Usage: Visualizes differences between versions

# Unstaged modifications
git diff

# Staged modifications
git diff --staged

# Compare with a commit
git diff HEAD~1

# Compare two branches
git diff main develop

# Compare a specific file
git diff HEAD -- index.html

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🟡 Intermediate Level

Branch Management

git branch - List and manage branches

Usage: Creation and management of development branches

# List local branches
git branch

# List all branches (local + remote)
git branch -a

# Create a new branch
git branch feature/login

# Delete a branch
git branch -d feature/login      # If merged
git branch -D feature/login      # Force deletion

# Rename current branch
git branch -m new-name

# Rename any branch
git branch -m old-name new-name

git checkout / git switch - Navigation

Usage: Move between branches or commits

# Classic method (checkout)
git checkout develop
git checkout -b feature/contact  # Create + switch

# Modern method (switch) - RECOMMENDED
git switch develop
git switch -c feature/contact    # Create + switch

# Return to previous branch
git switch -

# Move to a specific commit
git switch --detach abc1234

💡 Advice: Prefer git switch for navigation, git checkout for restoring files

git merge - Merge branches

Usage: Integrates modifications from one branch into another

# Merge feature/login into current branch
git merge feature/login

# Merge with custom message
git merge feature/login -m "Integration of login system"

# See already merged branches
git branch --merged
git branch --no-merged

🚨 In case of conflict:

# 1. Resolve conflicts in your editor
# 2. Mark as resolved
git add conflicted-file.js

# 3. Finalize the merge
git commit -m "resolve: conflict in login system"

Working with Remote Repositories

git remote - Manage remote repositories

Usage: Configures connections to external repositories

# List remotes
git remote -v

# Add a remote
git remote add origin https://github.com/user/repo.git

# Modify a remote URL
git remote set-url origin https://github.com/user/new-repo.git

# Remove a remote
git remote remove origin

git fetch - Retrieve without merging

Usage: Updates information about remote branches

# Fetch from origin
git fetch origin

# Fetch all remotes
git fetch --all

# Clean obsolete references
git fetch --prune

🎯 Difference: fetch retrieves, pull retrieves AND merges!

git pull - Retrieve and merge

Usage: Equivalent to git fetch + git merge

# Pull current branch
git pull

# Pull from a specific branch
git pull origin develop

# Pull with rebase
git pull --rebase origin main

git push - Send modifications

Usage: Publishes your commits to the remote repository

# Push current branch
git push

# Push with upstream definition
git push -u origin feature/login

# Push all branches
git push --all

# Push tags
git push --tags

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🔵 Advanced Level

Corrections and Advanced History

git reflog - Action history

Usage: Finds "lost" commits or past actions

# See complete action history
git reflog

# Reflog of a specific branch
git reflog show feature/login

# Recover a "lost" commit
git switch --detach HEAD@{3}
git branch recovery-branch HEAD@{3}

🆘 Emergency: Your last commit disappeared? git reflog is your friend!

git reset - Undo commits

Usage: Moves HEAD and modifies history

# Undo last commit (keep modifications)
git reset --soft HEAD~1

# Undo and remove modifications
git reset --hard HEAD~1

# Undo to a specific commit
git reset --hard abc1234

# Reset a specific file
git reset HEAD file.js

⚠️ Warning: --hard permanently deletes your modifications!

git restore - Restore files

Usage: Restores files to a previous state (replaces git checkout for files)

# Cancel file modifications
git restore index.html

# Restore from index (unstage)
git restore --staged index.html

# Restore from a specific commit
git restore --source=HEAD~1 index.html

git revert - Clean cancellation

Usage: Creates a new commit that undoes an existing commit

# Revert a specific commit
git revert abc1234

# Revert multiple commits
git revert HEAD~3..HEAD

# Revert without creating commit immediately
git revert --no-commit abc1234

✅ Advantage: Preserves history, ideal for shared branches!

Temporary Management

git stash - Temporary save

Usage: Sets aside modifications to return to them later

# Save modifications
git stash

# With descriptive message
git stash push -m "WIP: header refactoring"

# Include untracked files
git stash -u

# List stashes
git stash list

# Apply last stash
git stash pop

# Apply a specific stash
git stash apply stash@{1}

# Delete all stashes
git stash clear

💡 Typical usage: Switch branches quickly without commit!

Advanced Techniques

git cherry-pick - Apply selective commits

Usage: Copies a specific commit to the current branch

# Cherry-pick a commit
git cherry-pick abc1234

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

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

# Cherry-pick without automatic commit
git cherry-pick --no-commit abc1234

git rebase -i - History rewriting

Usage: Modifies, reorganizes, or merges commits interactively

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

# Rebase from a specific commit
git rebase -i abc1234

Options in editor:

• pick: keep the commit
• squash: merge with previous
• fixup: merge ignoring the message
• reword: modify only the message
• edit: modify the commit
• drop: delete the commit

Edit example:

pick abc1234 feat: add login
squash def5678 fix: typo in login
reword ghi9012 feat: complete system
drop jkl3456 test: debug commit

Conflict management:

# In case of conflict
git status                    # See conflicts
# Resolve in editor
git add resolved-file.js
git rebase --continue

# Abandon rebase
git rebase --abort

# Once finished, push modifications
git push -f

# If co-worker on same branch, secure their commits
git push --force-with-lease

⚠️ Important: Never rebase commits already pushed and shared!

Analysis and Debugging

git blame - Identify author

Usage: Shows who modified each line of a file

# Complete blame of a file
git blame index.html

# With more context
git blame -C index.html

# Between specific lines
git blame -L 10,20 index.html

git bisect - Binary search for bugs

Usage: Automatically finds the commit that introduced a bug

# Start bisect
git bisect start

# Mark current version as bad
git bisect bad

# Mark an earlier commit as good
git bisect good abc1234

# Git suggests a commit to test
# After testing, mark as good or bad
git bisect good    # or git bisect bad

# Repeat until finding the faulty commit

# End bisect
git bisect reset

Repository Maintenance

git gc - Cleanup and optimization

Usage: Optimizes the repository by compressing objects

# Basic cleanup
git gc

# Aggressive cleanup
git gc --aggressive --prune=now

# Check repository size
git count-objects -vH

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🔴 Expert Level

Release Management

git tag - Versioning and releases

Usage: Marks important points in history

# Create a lightweight tag
git tag v1.0.0

# Create an annotated tag (recommended)
git tag -a v1.0.0 -m "Version 1.0.0 - First stable release"

# Tag on a specific commit
git tag -a v0.9.0 abc1234

# List tags
git tag
git tag -l "v1.*"

# See tag details
git show v1.0.0

# Delete a local tag
git tag -d v1.0.0

# Push tags
git push origin v1.0.0      # Specific tag
git push origin --tags      # All tags
git push --follow-tags      # Tags + commits

# Delete a remote tag
git push origin :refs/tags/v1.0.0

Subprojects

git submodule - Nested repositories

Usage: Includes an external Git repository as a subfolder

# Add a submodule
git submodule add https://github.com/user/library.git libs/library

# Clone a project with submodules
git clone --recurse-submodules https://github.com/user/project.git

# Initialize submodules after clone
git submodule update --init --recursive

# Update a submodule
git submodule update --remote libs/library

# Update all submodules
git submodule foreach git pull origin main

git subtree - Alternative to submodules

Usage: Merges an external repository into a subfolder

# Add a subtree
git subtree add --prefix=libs/utils https://github.com/user/utils.git main --squash

# Update a subtree
git subtree pull --prefix=libs/utils https://github.com/user/utils.git main --squash

# Push modifications to the subtree
git subtree push --prefix=libs/utils https://github.com/user/utils.git main

Security and Integrity

Secure push with --force-with-lease

Usage: Force push that checks remote modifications

# Classic force push (DANGEROUS)
git push --force origin develop

# Secure force push (RECOMMENDED)
git push --force-with-lease origin develop

# With specific commit verification
git push --force-with-lease=develop:abc1234 origin develop

✅ Advantage: Avoids overwriting other developers' modifications!

Advanced Cleanup

Branch deletion and cleanup

Usage: Maintains a clean and organized repository

# Delete merged local branches with confirmation
git branch --merged | grep -v "\*\|main\|develop" | xargs -p -n 1 git branch -d

# Delete references to deleted remote branches
git remote prune origin

# See deleted remote branches
git branch -r --merged | grep origin | grep -v master | grep -v develop

# Delete a remote branch
git push origin --delete feature/old-feature

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📚 Recommended Workflows

🔄 Git Flow

# Feature branch
git switch develop
git switch -c feature/new-feature
# ... development ...
git push -u origin feature/new-feature
# ... pull request / merge request ...

# Release branch
git switch -c release/1.2.0 develop
# ... release preparation ...
git switch main
git merge release/1.2.0
git tag -a v1.2.0 -m "Release 1.2.0"

# Hotfix
git switch -c hotfix/critical-bug main
# ... correction ...
git switch main
git merge hotfix/critical-bug
git switch develop
git merge hotfix/critical-bug

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🎯 Best Practices

✅ Commit Messages

# Recommended format: type(scope): description
git commit -m "feat(auth): add OAuth login system"
git commit -m "fix(ui): fix header alignment on mobile"
git commit -m "docs(readme): update installation instructions"

# Conventional types:
# feat: new feature
# fix: bug fix
# docs: documentation
# style: formatting, no code change
# refactor: refactoring
# test: adding/modifying tests
# chore: maintenance tasks

🚀 Advanced Configuration

# Useful aliases
git config --global alias.co checkout
git config --global alias.br branch
git config --global alias.ci commit
git config --global alias.st status
git config --global alias.unstage 'reset HEAD --'
git config --global alias.last 'log -1 HEAD'
git config --global alias.visual '!gitk'

# Configure merge/diff tools
git config --global merge.tool vimdiff
git config --global diff.tool vimdiff

# Auto-correction of commands
git config --global help.autocorrect 1

# Colors
git config --global color.ui auto

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🆘 Emergency Situations

🚨 "I broke everything!"

# 1. See what happened
git reflog

# 2. Return to a previous state
git reset --hard HEAD@{2}

# 3. Or create a recovery branch
git branch recovery-branch HEAD@{2}

🔧 "My commit is on the wrong branch!"

# 1. Note the commit hash
git log --oneline -1

# 2. Undo the commit on current branch
git reset --hard HEAD~1

# 3. Go to the right branch
git switch right-branch

# 4. Cherry-pick the commit
git cherry-pick abc1234

🗑️ "I want to delete a file from all history!"

# WARNING: Rewrites all history!
git filter-branch --force --index-filter \
  'git rm --cached --ignore-unmatch secret-file.txt' \
  --prune-empty --tag-name-filter cat -- --all

# Modern version with git-filter-repo (recommended)
git filter-repo --path secret-file.txt --invert-paths

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📖 Additional Resources

• 📚 Official Git Documentation
• 🎮 Learn Git Branching
• 📝 Conventional Commits
• 🔧 Git Hooks

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"This guide accompanies you in your Git progression. From junior to expert, each command is a step towards mastery!"

✨ Created with passion by DorianABDS

👍 Thanks @DorianABDS for sharing.

💡 I suggest adding the -p option when using xargs when triggering a destructive command (like the one below that removes local branches merged into the current branch).
With the -p option, xargs will ask for confirmation before removing the branch.

Section: Branch deletion and cleanup

# Delete merged local branches
git branch --merged | grep -v "\*\|main\|develop" | xargs -p -n 1 git branch -d

You're welcome @ebouchut.
That's a good idea, I've added it 👍