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Git Reference: From Beginner to Pro

A comprehensive guide to Git commands and workflows.

References & Resources

Table of Contents

🚨 Houston, We Have a Commit History! 🚨

Below are tools for rewriting history, BUT remember the golden rule of Git:

NEVER rewrite a commit history that has already been pushed to a remote repository (unless you want to be the subject of office memes).

  • --amend
  • Rebase
  • Interactive rebase
  • reset

Creating & Inspecting Commits

Command Description
git init Initializes a new Git repository in the current directory.
git status Shows the status of files (modified, added, untracked) in the working directory and staging area.
git add <file> Stages a specific file to be included in the next commit.
git add <folder>/ Stages all files within a specified folder (and its subfolders).
git add . Stages all files in the current directory (and its subfolders).
git commit -m "message" Creates a new commit with the specified message.
git commit --amend Modifies the most recent commit, allowing you to change the commit message or add/remove staged changes.
git log Displays the commit history of the current branch.
git log --oneline --graph Shows a compact, graphical representation of the commit history.
git log -a --decorate --oneline --graph Visualizes your commit history as a beautiful ASCII graph. Perfect for understanding branch merges, rebases, and the overall flow of your project.
git show <commit> Displays the details of a specific commit (including changes made).
git reflog Shows a history of all actions that modified the tip of the current branch (e.g., commits, merges, rebases).
git blame <file> Shows who last modified each line of a file and in which commit.

Comparing & Viewing Changes

Command Description
git diff Shows the differences between the working directory and the staging area.
git diff --staged Shows the differences between the staging area and the last commit.
git diff HEAD~2 HEAD Shows the differences between the current commit and the commit two commits ago.
git diff branch1 branch2 Shows the differences between two branches.

Configuration

Command Description
git config --global user.name "Name" Sets your name for commits you make globally.
git config --global user.email "email" Sets your email for commits you make globally.

The Staging Area (The Index)

The staging area is a buffer between your working directory and the commit history. It allows you to select which changes to include in the next commit.

Working Directory => Staging Area Staging Area => Commit History Staging Area => Working Directory Remove Changes from Working Directory
git add <file> git commit -m "message" git reset <file> git restore <file>
git add <folder>/ git reset <folder>/ git restore <folder>/
git add . git reset git restore .

Additional Staged Changes Commands

Command Description
git add -p <file> Interactively choose which hunks (parts of changes) to add to the staging area.
git mv <old> <new> Moves or renames a file and stages the change.
git rm --cached <file> Removes a file from the staging area but keeps it in the working directory.

Working with GitHub

Command Description
git remote add origin <repository_url> Adds a remote repository named "origin" with the specified URL. Typically used when cloning a repository for the first time.
git remote -v Shows the URLs of your remote repositories.
git remote remove origin Removes the remote repository named "origin".
git push -u origin <branch_name> Pushes the specified branch to the "origin" remote and sets up tracking so you can simply use git push in the future.
git push --force-with-lease origin <branch> A safer alternative to git push --force, it will only push if the remote branch hasn't been updated since your last fetch.
git pull origin <branch_name> Fetches changes from the specified branch on the "origin" remote and merges them into your current branch.
git fetch origin Downloads all changes from the "origin" remote but doesn't merge them into your branches. Use git merge origin/<branch> to merge later if needed.

Undo Mistakes with Git (Like a Pro)

Git provides a powerful toolkit for fixing mistakes. Here's how to handle common scenarios:

Understanding the Basics

  • Hunks and Chunks:
    • Hunk: A section of code that's been changed within a file (like a paragraph).
    • Chunk: A smaller piece of a hunk (like a sentence).
  • Inspecting Changes: Always start by using git diff <file> to see the differences between versions before undoing anything.

Discarding Uncommitted Changes

  • Restore a Single File: git restore <file> (Caution: This is irreversible!)
  • Restore a Deleted File (Before Committing): git restore <file>
  • Discard Part of a File's Changes: git restore -p <file> (Interactively select hunks/chunks to discard)
  • Discard All Uncommitted Changes: git restore . (Caution: This affects all files!)

Modifying Existing Commits

  • Amend Last Commit: git commit --amend -m "New message" (Changes message or content of the most recent commit. Avoid using on pushed commits.)
  • Revert a Specific Commit: git revert <commit_id> (Creates a new commit that undoes the changes of the specified commit. Safe for pushed commits.)

Resetting to an Older State (Use with Caution!)

  • Resetting the Entire Branch:
    • git reset --hard <commit_id>: Discards all changes made after the specified commit. (Caution: Can cause data loss!)
    • git reset --mixed <commit_id>: Keeps changes made after the specified commit but unstages them.
  • Resetting a Single File:
    • git log <file>: Find the commit ID you want to revert to.
    • git restore --source=<commit_id> <file>: Restores the file to the state it was in at that commit.

Fixing Pushed Mistakes

  • Creating a New Branch from a Mistaken Commit:
    • git branch <new_branch_name> <mistaken_commit_id>
  • Removing the Commit from the Original Branch:
    • git reset HEAD~1 --hard (Only if the mistaken commit is the most recent one)
  • Moving a Commit to a Different Branch (Cherry-Picking):
    • git checkout <target_branch>
    • git cherry-pick <commit_id>

Interactive Rebase (Advanced)

  • Rewriting Commit History: git rebase -i <commit_id> (Allows for editing, squashing, reordering, or dropping commits. Avoid on pushed commits!)
  • Fixing Previous Commits:
    • Make your changes.
    • git add <changed_files>
    • git commit --fixup=<commit_id_to_fix>
    • git rebase -i --autosquash <base_commit> (Squashes the fixup commit into the original)

Important Note: Rewriting commit history (with --amend, rebase, interactive rebase, or reset) on commits that have been pushed to a shared repository can cause serious problems for your collaborators. Use these commands with caution!

Branches & History

Command Description
git branch Lists all local branches.
git branch <branch_name> Creates a new branch.
git checkout <branch_name> Switches to the specified branch.
git switch -c <branch_name> Creates a new branch and switches to it.
git merge <branch_name> Merges the specified branch into the current branch.
git rebase <branch_name> Rebases the current branch onto the specified branch, creating a linear history.
git revert <commit> Creates a new commit that undoes the changes introduced by the specified commit.
git cherry-pick <commit> Applies the changes from the specified commit onto the current branch.

Advanced Commit Manipulation

Command Description
git commit -m "message" --amend Modifies the most recent commit's message or staged changes.
git revert <commit> Creates a new commit that undoes the changes made in a specific commit. This is a safer way to undo changes than resetting, as it doesn't alter the existing commit history.
git reset --hard <commit> Resets the current branch to a specified commit, discarding all changes made after that commit. This should be used with caution, as it can result in data loss.
git reset --mixed <commit> Resets the current branch to a specified commit, but keeps the changes made after that commit in the working directory (unstages them). This is the default behavior of git reset.
git cherry-pick <commit> Applies the changes from a specific commit onto the current branch. Useful for selectively applying changes from other branches.
git rebase -i <commit> Starts an interactive rebase, allowing you to modify, combine, or reorder commits.
git commit --fixup <commit> Creates a commit that is intended to fix a previous commit. When used with git rebase -i --autosquash, it will automatically move the fixup commit next to the commit it's fixing and suggest squashing them together.

Working with Remotes

Command Description
git fetch Fetches all branches and their commits from a remote repository without merging them.
git pull Combines git fetch and git merge, downloading changes from a remote repository and immediately merging them into your current branch.
git stash Temporarily saves changes that are not ready to be committed.
git stash pop Restores the most recently stashed changes to the working directory.

Additional Tools & Tips

  1. git diff <file>: Shows changes made to a specific file within your working directory.
  2. git restore:
    • git restore <file>: Restores a deleted file or discards changes in a file.
    • git restore -p <file>: Interactively select hunks to restore or discard in a file.
    • git restore .: Discards all uncommitted changes in the working directory.
  3. Branch from a Specific Commit: git branch <new_branch_name> <commit_id>
  4. Checkout with Precision: Use git checkout <branch/commit> <file/folder> to revert files to a specific state or copy them from another branch.
  5. git show-branch: Displays detailed information about all branches, including their commits and relationships.
  6. git log --follow <file>: Shows the commit history of a file, even if it was renamed or moved.

Let me know if you'd like any further refinements or additions to this cheat sheet!