Reflog for finding lost commits in Git - Practice Problems & Coding Challenges

Challenge - 5 Problems

💻 Command Output

intermediate

What does the command git reflog show?

You run git reflog in your repository. What output do you expect to see?

Git

git reflog

A A list of recent HEAD positions with commit hashes and messages.

B A list of all tags in the repository.

C The current status of files in the working directory.

D A list of all branches and their remote tracking status.

💡 Hint

Think about what 'reflog' tracks in Git.

git reflog shows a history of where HEAD has pointed recently, including commits you may have lost track of.

💻 Command Output

intermediate

What is the output of git reflog show HEAD@{2}?

Assuming your reflog has at least 3 entries, what does this command display?

Git

git reflog show HEAD@{2}

A The commit details of the third most recent HEAD position.

B The current commit hash and message.

C An error saying the reflog entry does not exist.

D A list of all commits in the repository.

💡 Hint

HEAD@{n} refers to the nth previous position of HEAD.

HEAD@{2} means the HEAD position two moves ago, so this shows that commit's details.

🔀 Workflow

advanced

How to recover a lost commit using reflog?

You accidentally reset your branch and lost a commit. Which sequence of commands correctly recovers the lost commit using reflog?

A 1,3,2,4

B 1,2,3,4

C 2,1,3,4

D 1,4,3,2

💡 Hint

First find the commit, then create a branch from it.

First, use git reflog to find the lost commit hash. Then checkout that commit, create a new branch, and switch to it.

❓ Troubleshoot

advanced

Why does git reflog not show a lost commit?

You lost a commit but git reflog does not list it. What is the most likely reason?

A The commit is hidden because the branch was deleted.

B The commit was never created in the repository.

C The reflog only shows remote branch history, not local commits.

D The reflog expired or was cleaned and no longer tracks that commit.

💡 Hint

Reflog entries expire after some time or cleanup.

Reflog entries expire after a default time (usually 90 days) or can be cleaned manually, so old commits may disappear from reflog.

✅ Best Practice

expert

What is the best practice to avoid losing commits that reflog might not recover?

Which option is the best practice to ensure commits are not lost even if reflog expires or is cleaned?

A Use <code>git reset --hard</code> frequently to clean history.

B Rely solely on reflog to find lost commits when needed.

C Regularly push commits to a remote repository to back them up.

D Delete branches immediately after merging to keep history clean.

💡 Hint

Think about how to keep commits safe beyond local history.

Pushing commits to a remote repository backs them up safely, preventing loss even if local reflog is cleaned.

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