Module 10 Lesson 3: The git reflog for disaster recovery

We’ve all been there: You ran a git reset --hard by mistake. You deleted a branch that you thought was merged, but it wasn't. You was in the middle of a rebase and everything went wrong.

You think your work is gone forever. It isn't.

In this lesson, we learn about the Reference Log (reflog)—Git's ultimate "Safety Net."

1. What is the Reflog?

While the git log shows you the history of the commits in a branch, the git reflog shows you the history of your actions.

Every time you:

Switch branches
Make a commit
Amend a commit
Pull from a server
Reset a branch

Git records that action in a local, private list. This log is not shared with your team; it only exists on your machine.

2. Navigating the Reflog

To see your recent history:

git reflog

Reading the output:

8f3d12a HEAD@{0}: reset: moving to HEAD~1
7a9b4c2 HEAD@{1}: commit: Add database logic
a1c2b3d HEAD@{2}: checkout: moving from main to feature-x

The numbers in the brackets (HEAD@{0}, HEAD@{1}) tell you how many steps ago that action happened.

3. The Resurrection: How to Recover

Imagine you accidentally "deleted" the commit 7a9b4c2 (Add database logic) by resetting. To bring it back:

# 1. Find the ID in the reflog
# 2. Reset back to it
git reset --hard 7a9b4c2

Or, if you accidentally deleted a branch, you can recreate it at the exact commit it was at before the deletion:

git branch feature-restored 7a9b4c2

graph TD
    Mistake["Accident (Reset / Delete)"]
    Reflog["git reflog"]
    ID["Find Commitment SHA-1"]
    Restore["git reset --hard [SHA-1]"]
    
    Mistake --> Reflog
    Reflog --> ID
    ID --> Restore
    Restore --> Happy["Project Recovered!"]

4. The Time Limit

The reflog is not infinite. Git periodically cleans it up (garbage collection). By default, reflog entries are kept for:

90 days for reachable commits.
30 days for unreachable (abandoned) commits.

So, if you make a mistake, you have about a month to realize it and fix it using the reflog!

Lesson Exercise

Goal: The Controlled Disaster.

Go to your git-practice repo.
Make a change to a file and commit it.
Now, run git reset --hard HEAD~1 to "delete" that commit.
Run git log. Observe that the commit is gone.
Run git reflog. Find the line where you made the commit (it should look like commit: Message...).
Run git reset --hard <SHA-1> from that line.
Run git log again. Is the commit back? (It should be!).

Observation: You'll realize that as long as you have committed your code at least once, Git effectively makes it impossible to lose your work on accident.

Summary

In this lesson, we established:

git reflog tracks every pointer movement on your local machine.
It is your primary tool for recovering after a reset --hard or a branch deletion.
It is local and temporary (30-90 days).
Knowing the reflog exists significantly reduces "Git Anxiety."

Next Lesson: Want Git to automatically test your code before you commit? Welcome to Lesson 4: Git hooks: Automating your local environment.