Scenario 4 — Recover Lost Commits with Reflog

The brief

Deliberately "lose" commits via reset and rebase, then recover them using reflog. Build the muscle memory for the safety net.

Step 1: Setup (5 min)

mkdir reflog-drill && cd reflog-drill
git init
echo "v1" > app.py && git add . && git commit -m "Initial"
echo "v2" > app.py && git commit -am "Improve"
echo "v3" > app.py && git commit -am "Add feature"
echo "v4" > app.py && git commit -am "Refactor"
echo "v5" > app.py && git commit -am "Polish"

git log --oneline
# abc1 Polish
# abc2 Refactor
# abc3 Add feature
# abc4 Improve
# abc5 Initial

Step 2: Lose via reset --hard (10 min)

git reset --hard HEAD~3
# Lost: Polish, Refactor, Add feature
# HEAD now at abc4 Improve

git log --oneline
# abc4 Improve
# abc5 Initial

cat app.py
# v2

The last 3 commits and the v3-v5 content seem gone. But:

git reflog
# abc4 HEAD@{0}: reset: moving to HEAD~3
# abc1 HEAD@{1}: commit: Polish
# abc2 HEAD@{2}: commit: Refactor
# abc3 HEAD@{3}: commit: Add feature
# abc4 HEAD@{4}: commit: Improve
# abc5 HEAD@{5}: commit (initial): Initial

Each operation logged. Restore:

git reset --hard abc1     # the Polish commit
# OR
git reset --hard HEAD@{1}  # same effect

git log --oneline
# abc1 Polish
# abc2 Refactor
# abc3 Add feature
# abc4 Improve
# abc5 Initial

cat app.py
# v5

Recovered.

Step 3: Lose via interactive rebase mistake (10 min)

git rebase -i HEAD~3

Mark all as drop (mistake!):

drop abc1 Polish
drop abc2 Refactor
drop abc3 Add feature

Save. Git executes; commits gone:

git log --oneline
# abc4 Improve
# abc5 Initial

Recover via reflog:

git reflog
# Look for: rebase (start): checkout abc4 (pre-rebase state)
# Or: the SHA of where you were before rebase

git reset --hard <pre-rebase-sha>
# Or: git reset --hard ORIG_HEAD  (Git sets ORIG_HEAD before destructive ops)

ORIG_HEAD is a convenient shortcut for the position before the last "big" operation.

Step 4: Recover a deleted branch (5 min)

git switch -c feature
echo "feature work" > feature.txt
git add . && git commit -m "Feature commit"

git switch main
git branch -D feature
# Deleted branch feature (was abc7).

git branch
# Only main shown; feature gone

But the commit still exists:

git reflog
# abc7 HEAD@{2}: commit: Feature commit
# ...

git branch feature abc7    # recreate branch at that commit
git switch feature
cat feature.txt
# feature work

Step 5: Use fsck for truly lost commits

Simulate an old loss (in real life, after reflog expired):

git fsck --lost-found
# dangling commit abc8 ...

These are commits not referenced by any branch or in reflog. Investigate:

git show abc8
# See its diff and message

git branch recovered abc8

Step 6: Reflog scope

git reflog                  # HEAD's reflog
git reflog main             # main branch's reflog
git reflog --all            # all refs' reflog

Branches have their own reflog. If you reset main and want history of main specifically:

git reflog main
# Specifically tracks main's tip history

Deliverables

Submission contract: upload RECOVERY.md (reflog retention, ORIG_HEAD, fsck --lost-found, what can't be recovered).

100-pt rubric: reset --hard recovery (25) / rebase-mistake recovery via reflog/ORIG_HEAD (25) / deleted-branch recovery (20) / fsck dangling-commit recovery (15) / RECOVERY.md documents limits (15).

upload RECOVERY.md (reflog retention, ORIG_HEAD, fsck --lost-found, what can't be recovered).

reset --hard recovery (25) / rebase-mistake recovery via reflog/ORIG_HEAD (25) / deleted-branch recovery (20) / fsck dangling-commit recovery (15) / RECOVERY.md documents limits (15).