Recovering lost commits with reflog in Git - Step-by-Step Execution

Process Flow - Recovering lost commits with reflog

Make commits

↓

Commit lost or detached

↓

Run git reflog

↓

Find lost commit hash

↓

Use git checkout or git reset to recover

↓

Lost commit restored

This flow shows how git records all HEAD moves in reflog, allowing you to find and recover lost commits by checking the reflog and resetting or checking out the commit.

Execution Sample

Git

git reflog
# shows recent HEAD changes

git reset --hard <commit-hash>
# recovers lost commit by resetting HEAD

This code lists recent HEAD changes and resets the branch to a lost commit using its hash.

Process Table

Step	Command	Action	Result	Notes
1	git commit -m 'Initial commit'	Create commit	Commit abc123 created	Commit saved in branch and reflog
2	git commit -m 'Second commit'	Create commit	Commit def456 created	Commit saved in branch and reflog
3	git reset --hard abc123	Move HEAD back	HEAD now at abc123	Second commit lost from branch but in reflog
4	git reflog	Show HEAD history	Shows abc123 and def456 entries	Lost commit def456 visible here
5	git reset --hard def456	Recover lost commit	HEAD now at def456	Lost commit restored to branch
6	git reflog	Show HEAD history	Shows current HEAD at def456	Recovery complete

💡 Lost commit recovered by resetting HEAD to commit hash found in reflog

Status Tracker

Variable	Start	After Step 1	After Step 2	After Step 3	After Step 5	Final
HEAD	none	abc123	def456	abc123	def456	def456
Branch pointer	none	abc123	def456	abc123	def456	def456
Reflog entries	empty	abc123	abc123, def456	abc123, def456	abc123, def456	abc123, def456

Key Moments - 3 Insights

Why does the lost commit still appear in reflog after a hard reset?

Because reflog records all HEAD movements, including resets, so the lost commit hash remains accessible even if it's no longer on a branch (see Step 4 in execution_table).

Can I recover a commit if I don't know its hash?

Yes, by running 'git reflog' you can see recent commit hashes and find the lost commit hash to recover it (see Step 4).

What happens if I reset to a commit not in reflog?

Git will succeed if the commit hash is valid and exists in the repository; reflog only helps locate recent lost commits, but reset works with any valid commit hash.

Visual Quiz - 3 Questions

Look at the execution table, what is the HEAD value after Step 3?

A def456

B abc123

C none

D xyz789

💡 Hint

Check the 'HEAD' row in variable_tracker after Step 3

At which step does the lost commit get restored to the branch?

A Step 2

B Step 3

C Step 5

D Step 6

💡 Hint

Look for the 'Recover lost commit' action in execution_table

If you skip running 'git reflog', what would happen when trying to recover a lost commit?

A You won't know the commit hash to reset to

B Git automatically recovers lost commits

C You can still recover without the hash

D The lost commit is deleted permanently

💡 Hint

Refer to key_moments about finding commit hashes using reflog

Concept Snapshot

git reflog records all HEAD moves including resets
Use 'git reflog' to find lost commit hashes
Recover lost commits with 'git reset --hard <commit-hash>'
Reflog helps undo mistakes like hard resets
Lost commits remain accessible until reflog expires

Full Transcript

This lesson shows how git reflog tracks all changes to HEAD, including commits and resets. When a commit is lost due to a hard reset, it still appears in reflog. By running 'git reflog', you can find the lost commit's hash. Then, using 'git reset --hard <commit-hash>', you can restore the lost commit to your branch. The execution table traces creating commits, resetting HEAD, viewing reflog, and recovering the lost commit. Variables like HEAD and branch pointers change accordingly. Key moments clarify why reflog keeps lost commits and how to find hashes. The quiz tests understanding of HEAD values, recovery steps, and the importance of reflog. The snapshot summarizes the commands and concepts for quick reference.

Practice

1. What is the primary purpose of git reflog in Git?

easy

A. To show a log of where HEAD and branch references have been recently

B. To permanently delete commits from the repository

C. To merge two branches automatically

D. To push commits to a remote repository

Solution

1. Step 1: Understand what reflog tracks

   Git reflog records changes to HEAD and branch tips, showing recent commit movements.

2. Step 2: Identify reflog's main use

   It helps find lost commits by listing recent HEAD positions, not deleting or merging.

3. Final Answer:

   To show a log of where HEAD and branch references have been recently -> Option A

4. Quick Check:

   Reflog = recent HEAD changes [OK]

Hint: Reflog shows recent HEAD moves, not branch merges or deletions [OK]

Common Mistakes:

• Confusing reflog with git log
• Thinking reflog deletes commits
• Assuming reflog pushes commits

2. Which command correctly recovers a lost commit using its reflog hash abc1234 by creating a new branch named recovered?

easy

A. git branch recovered && git checkout abc1234

B. git reset --hard recovered abc1234

C. git reflog checkout abc1234 recovered

D. git checkout -b recovered abc1234

Solution

1. Step 1: Understand how to create a branch from a commit hash

   The command git checkout -b <branch> <commit> creates and switches to a new branch at that commit.

2. Step 2: Check each option's correctness

   git checkout -b recovered abc1234 uses correct syntax. git branch recovered && git checkout abc1234 creates branch but checks out commit separately (detached HEAD). git reflog checkout abc1234 recovered is invalid syntax. git reset --hard recovered abc1234 misuses reset.

3. Final Answer:

   git checkout -b recovered abc1234 -> Option D

4. Quick Check:

   Create branch from commit: checkout -b [OK]

Hint: Use 'git checkout -b branch commit' to recover lost commit [OK]

Common Mistakes:

• Using git reflog checkout (invalid command)
• Creating branch and checkout separately causing detached HEAD
• Misusing git reset syntax

3. Given the following reflog output snippet:

abc1234 HEAD@{0}: commit: Fix typo
def5678 HEAD@{1}: commit: Add feature
789abcd HEAD@{2}: commit: Initial commit

What command will restore the commit with message 'Add feature'?

medium

A. git checkout HEAD@{2}

B. git checkout 789abcd

C. git checkout def5678

D. git checkout abc1234

Solution

1. Step 1: Identify the commit hash for 'Add feature'

   From reflog, 'Add feature' commit hash is def5678 at HEAD@{1}.

2. Step 2: Use git checkout with the correct hash

   Checking out def5678 restores that commit state.

3. Final Answer:

   git checkout def5678 -> Option C

4. Quick Check:

   Checkout commit by hash = def5678 [OK]

Hint: Match commit message to hash, then checkout that hash [OK]

Common Mistakes:

• Choosing wrong commit hash
• Using HEAD@{2} which is 'Initial commit'
• Confusing latest commit with target commit

4. You ran git reflog and found a lost commit hash abc1234. You tried git checkout abc1234 but got a detached HEAD warning. How do you fix this to recover the commit safely?

medium

A. Create a new branch at that commit using git checkout -b recovered abc1234

B. Run git reset --hard abc1234 immediately

C. Delete the reflog entry and try again

D. Push the commit hash to remote

Solution

1. Step 1: Understand detached HEAD state

   Checking out a commit hash puts you in detached HEAD, which is risky for new work.

2. Step 2: Create a branch to save the commit safely

   Use git checkout -b recovered abc1234 to create a branch and avoid losing commits.

3. Final Answer:

   Create a new branch at that commit using git checkout -b recovered abc1234 -> Option A

4. Quick Check:

   Fix detached HEAD by creating branch [OK]

Hint: Always create a branch from lost commit to avoid detached HEAD [OK]

Common Mistakes:

• Ignoring detached HEAD and continuing work
• Deleting reflog entries mistakenly
• Trying to push without branch

5. You accidentally reset your branch to an older commit, losing recent commits. You run git reflog and see:

abc1234 HEAD@{0}: reset: moving to abc1234
def5678 HEAD@{1}: commit: Add new feature
789abcd HEAD@{2}: commit: Fix bug

How do you restore your branch to include the lost 'Add new feature' commit?

hard

A. Delete reflog entries before abc1234

B. Run git reset --hard def5678 to move branch back to lost commit

C. Run git checkout abc1234 to stay at reset point

D. Run git merge def5678 from abc1234

Solution

1. Step 1: Identify lost commit hash from reflog

   The lost commit 'Add new feature' is at def5678 (HEAD@{1}).

2. Step 2: Use git reset to move branch pointer back

   Running git reset --hard def5678 restores branch to that commit, recovering lost work.

3. Final Answer:

   Run git reset --hard def5678 to move branch back to lost commit -> Option B

4. Quick Check:

   Reset branch to lost commit hash [OK]

Hint: Use git reset --hard with reflog hash to recover lost commits [OK]

Common Mistakes:

• Checking out reset commit instead of resetting branch
• Deleting reflog entries unnecessarily
• Trying to merge without branch pointer