Reflog for finding lost commits in Git - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is git reflog used for?

git reflog shows a log of where your HEAD and branches have been. It helps you find commits that seem lost or unreachable.

beginner

How does git reflog help recover lost commits?

It records every change to HEAD, so you can find the commit hash of lost commits and restore them by checking out or resetting to that hash.

intermediate

What command would you use to reset your branch to a lost commit found in reflog?

You use git reset --hard <commit-hash> to move your branch pointer back to the lost commit.

beginner

True or False: git reflog only shows commits that are part of the current branch.

False. git reflog tracks all HEAD movements, including commits from other branches or detached HEAD states.

intermediate

What is the difference between git log and git reflog?

git log shows the commit history of the current branch. git reflog shows all recent changes to HEAD, including commits that might not be in the current branch history.

What does git reflog record?

A All changes to HEAD and branch pointers

B Only commits pushed to remote

C Only commits merged into main branch

D Only uncommitted changes

git reflog records all changes to HEAD and branch pointers, helping track lost commits.

Which command helps you restore a lost commit found in reflog?

A git checkout <commit-hash>

B git push origin main

C git merge <commit-hash>

D git stash pop

You can use git checkout <commit-hash> to view or restore a lost commit found in reflog.

If you want to move your branch pointer back to a lost commit, which command is best?

A git commit --amend

B git reset --hard <commit-hash>

C git branch -d <branch-name>

D git fetch origin

git reset --hard <commit-hash> moves your branch pointer to the lost commit.

Does git reflog show commits that are not reachable by any branch?

A Only commits pushed to remote

B No, only commits on branches

C Yes, it tracks all HEAD movements

D Only commits merged into main

git reflog tracks all HEAD movements, including commits not reachable by any branch.

What is the main difference between git log and git reflog?

A <code>git log</code> shows stash history; <code>git reflog</code> shows branch history

B <code>git log</code> shows uncommitted changes; <code>git reflog</code> shows commits

C <code>git log</code> shows remote commits; <code>git reflog</code> shows local commits

D <code>git log</code> shows commit history; <code>git reflog</code> shows HEAD changes

git log shows commit history of the branch; git reflog shows all HEAD changes including lost commits.

Explain how you would use git reflog to find and recover a lost commit.

Think about how reflog tracks HEAD movements and how to move your branch pointer.

Describe the difference between git log and git reflog and why reflog is useful for recovering lost commits.

Consider what each command tracks and their purpose.

Practice

1. What is the primary purpose of git reflog?

easy

A. To list all remote branches

B. To permanently delete commits from the repository

C. To record where HEAD and branches have pointed recently

D. To merge two branches automatically

Solution

1. Step 1: Understand what reflog tracks

   Reflog records the history of where HEAD and branch references have pointed, including commits that might be lost after resets or rebases.

2. Step 2: Compare options with reflog purpose

   Only To record where HEAD and branches have pointed recently correctly describes reflog's role. Options B, C, and D describe unrelated git functions.

3. Final Answer:

   To record where HEAD and branches have pointed recently -> Option C

4. Quick Check:

   Reflog tracks HEAD history = A [OK]

Hint: Reflog shows recent HEAD moves, like a safety net [OK]

Common Mistakes:

• Confusing reflog with git log
• Thinking reflog deletes commits
• Assuming reflog lists remote branches

2. Which command correctly shows the reflog entries?

easy

A. git reflog

B. git reflog list

C. git reflog -a

D. git reflog --show

Solution

1. Step 1: Recall the basic reflog command

   The simplest and correct command to show reflog entries is git reflog.

2. Step 2: Evaluate other options

   git reflog --show is invalid; git reflog list and git reflog -a are invalid commands.

3. Final Answer:

   git reflog -> Option A

4. Quick Check:

   Basic reflog command = git reflog [OK]

Hint: Use just 'git reflog' to see recent HEAD moves [OK]

Common Mistakes:

• Adding unnecessary subcommands like 'list'
• Using invalid flags like '-a'
• Confusing reflog with git log

3. After running git reset --hard HEAD~1, you realize you lost a commit. Which command helps you find the lost commit's hash?

medium

A. git reflog

B. git status

C. git branch

D. git log --oneline

Solution

1. Step 1: Understand what happens after reset

   git reset --hard HEAD~1 moves HEAD back one commit, making the latest commit unreachable but still in reflog.

2. Step 2: Identify command to find lost commit

   git reflog shows recent HEAD positions including the lost commit's hash. Other commands won't show unreachable commits.

3. Final Answer:

   git reflog -> Option A

4. Quick Check:

   Reflog shows lost commits after reset = C [OK]

Hint: Use reflog to find commits lost by reset [OK]

Common Mistakes:

• Using git status which shows working tree only
• Using git branch which lists branches, not commits
• Using git log which hides unreachable commits

4. You ran git reset --hard HEAD~2 but want to restore the latest commit. Which command correctly resets to the lost commit using reflog?

medium

A. git reset --hard HEAD@{2}

B. git reset --hard origin/main

C. git reset --hard HEAD~1

D. git reset --hard HEAD@{1}

Solution

1. Step 1: Understand reflog indexing

   After resetting HEAD back two commits, reflog entries show HEAD@{0} as current, HEAD@{1} as previous position (the lost commit), and HEAD@{2} as older.

2. Step 2: Choose correct reflog entry to restore

   To restore the latest lost commit, reset to HEAD@{1} which points to it. HEAD@{2} is older, HEAD~1 is relative to current HEAD, and origin/main may differ.

3. Final Answer:

   git reset --hard HEAD@{1} -> Option D

4. Quick Check:

   Use HEAD@{1} to restore last HEAD position [OK]

Hint: Reset to HEAD@{1} to undo last reset [OK]

Common Mistakes:

• Using HEAD@{2} which is older than needed
• Using HEAD~1 which is relative to current HEAD
• Resetting to origin/main which may differ

5. You accidentally deleted a branch with important commits. How can you recover the lost commits using reflog?

hard

A. Run git branch -d to restore the branch

B. Find the commit hash in git reflog and create a new branch at that hash

C. Use git reset --hard origin/branch-name to recover commits

D. Re-clone the repository to get the branch back

Solution

1. Step 1: Locate lost commits in reflog

   Deleted branch commits remain in reflog as recent HEAD positions or branch references before deletion.

2. Step 2: Create a new branch at the lost commit hash

   After finding the commit hash in reflog, use git branch new-branch-name <commit-hash> to restore the branch with lost commits.

3. Final Answer:

   Find the commit hash in git reflog and create a new branch at that hash -> Option B

4. Quick Check:

   Reflog + new branch recovers deleted commits [OK]

Hint: Use reflog hash to recreate deleted branch [OK]

Common Mistakes:

• Trying to delete branch again to restore it
• Resetting to origin which may not have deleted commits
• Re-cloning loses local lost commits