Lesson 2: The Undo Button

Everyone makes mistakes. The true power of Git is not just saving history — it's undoing mistakes safely. Git has multiple "undo" tools, each for a different situation.

The Undo Toolbox

Situation                          →  Solution
───────────────────────────────────────────────────
Staged a file by accident          →  git restore --staged <file>
Want to discard local changes      →  git restore <file>
Committed but want to undo         →  git revert <commit>
Need to go back to a past state    →  git reset <commit>

1. Unstaging: git restore --staged

You ran git add on a file you didn't mean to stage. Remove it from staging without losing your changes:

git restore --staged readme.txt

The file goes back to "modified" status — your edits are safe.

2. Discarding Changes: git restore

You made changes to a file and want to throw them away entirely:

git restore readme.txt

⚠️ Warning: This is destructive! The changes are gone forever. There's no undo for the undo.

3. Reverting a Commit: git revert

You committed something bad. git revert creates a new commit that undoes the changes — without erasing history.

git revert HEAD              # Undo the most recent commit
git revert abc123            # Undo a specific commit

This is the safe way to undo in a shared repository.

4. Resetting (Advanced): git reset

git reset moves the branch pointer backward. It comes in three flavors:

| Mode | Command | Effect | |------|---------|--------| | Soft | git reset --soft HEAD~1 | Undo commit, keep changes staged | | Mixed | git reset HEAD~1 | Undo commit, keep changes in working dir | | Hard | git reset --hard HEAD~1 | ⚠️ Undo commit AND delete all changes |

Rule of Thumb: Use revert for shared branches. Use reset only on your personal branches.

Mission Objective

Practice your undo skills:

1. Unstage: Run git restore --staged readme.txt to remove a file from staging.
2. Discard: Run git restore readme.txt to throw away local changes.
3. Revert: Run git revert HEAD --no-edit to safely undo the last commit.

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DevOps Scenario

In a CI/CD pipeline, if a bad commit gets deployed to production, you git revert it immediately. This creates a clean undo that everyone can see in the history — no confusion, no deleted evidence.