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Chapter 4 — Undoing Things

Git gives you many ways to undo mistakes. The right tool depends on where the mistake is.

Undo Cheatsheet

Mistake is in...             Use...
─────────────────────────────────────────
Working directory            git checkout -- <file>  or  git restore <file>
Staging area                 git reset HEAD <file>   or  git restore --staged <file>
Last commit (not pushed)     git commit --amend
Older commit (not pushed)    git rebase -i
Any commit (already pushed)  git revert

Discard Changes in Working Directory

Example: Throw away uncommitted edits

echo "BROKEN CODE" > index.js
git status
Changes not staged for commit:
        modified:   index.js

git restore index.js
cat index.js
console.log('hello');
function greet() { return 'hi'; }

🧠 What happened? git restore replaced the working directory version with the version from the staging area (which matches the last commit). Your changes are gone — this is not reversible.

Unstage a File

Example: Remove a file from the staging area

echo "secret=abc123" > .env
git add .env        # Oops, didn't mean to stage this
git restore --staged .env
git status
Untracked files:
        .env

🧠 What happened? The file is still on disk, but it's no longer staged for commit. Your changes are safe.

Amend the Last Commit

Example: Fix a typo in the last commit message

git commit --amend -m "Add greet function to index.js"

Example: Add a forgotten file to the last commit

echo "test" > test.js
git add test.js
git commit --amend --no-edit

🧠 What happened? --amend replaces the last commit with a new one. The old commit is discarded. Never amend commits you've already pushed — it rewrites history.

Revert a Commit

Example: Undo a commit that's already been pushed

git log --oneline
c3d4e5f Add broken feature
e4f5a6b Add greet function
a1b2c3d Initial commit

git revert c3d4e5f
[main f6g7h8i] Revert "Add broken feature"
 1 file changed, 1 deletion(-)

git log --oneline
f6g7h8i Revert "Add broken feature"
c3d4e5f Add broken feature
e4f5a6b Add greet function
a1b2c3d Initial commit

🧠 What happened? git revert creates a new commit that undoes the changes from the target commit. History is preserved. This is the safe way to undo public commits.

Reset: Moving the Branch Pointer

Reset is powerful and comes in three flavors:

                     Moves HEAD?  Resets Index?  Resets Working Dir?
git reset --soft         ✅           ❌               ❌
git reset --mixed        ✅           ✅               ❌
git reset --hard         ✅           ✅               ✅

Example: Soft reset — undo commit, keep changes staged

git reset --soft HEAD~1
git status
Changes to be committed:
        modified:   index.js

🧠 What happened? The commit is gone, but your changes are still staged. Useful when you want to re-do a commit.

Example: Mixed reset (default) — undo commit, unstage changes

git reset HEAD~1
git status
Changes not staged for commit:
        modified:   index.js

Example: Hard reset — undo everything

git reset --hard HEAD~1

⚠️ Warning: --hard permanently discards uncommitted changes. Use with extreme care.

Example: Reset to a specific commit

git reset --hard a1b2c3d

🧠 What happened? Your branch now points to a1b2c3d. All commits after it are orphaned (but recoverable via git reflog for ~30 days).

Clean: Remove Untracked Files

Example: See what would be deleted

git clean -n
Would remove temp.txt
Would remove debug.log

Example: Actually delete them

git clean -f

Example: Remove untracked directories too

git clean -fd

← Chapter 3: Viewing History · Next: Chapter 5 — Branches →