Undo and Recovery¶

By Sameer Alam · Updated 14 September 2026

What You'll Learn¶

• Which undo command to use for each situation, and which ones rewrite history
• The difference between reset and revert, and why it matters once you've pushed
• How to recover commits you think you've lost, using the reflog
• How to move commits with cherry-pick, park work with stash, and find bugs with bisect

The Golden Rule¶

Rewrite only history nobody else has. Before pushing, you can amend, reset, and rebase freely. After others may have pulled a commit, undo it by adding a new commit with git revert.

Pick the Right Command¶

Working Tree and Staging¶

git restore src/app.py                 # discard unstaged edits to one file
git restore .                          # discard all unstaged edits (careful)
git restore --staged src/app.py        # unstage, keep edits
git restore --source=HEAD~3 src/app.py # bring back the file as it was three commits ago
git clean -nd                          # preview untracked files that would be deleted
git clean -fd                          # delete them

git restore and git clean -f delete work that was never committed, and Git can't recover it. Always preview with git clean -n.

Amend the Last Commit¶

git add forgotten_test.py
git commit --amend --no-edit           # add to the previous commit, keep its message
git commit --amend -m "Better message" # change the message

If you already pushed the commit to your own feature branch, follow up with git push --force-with-lease.

Reset: Move the Branch Pointer¶

git reset <commit> moves the current branch to <commit>. The mode decides what happens to the changes from the commits you moved past:

flowchart LR
  subgraph soft["--soft"]
    S1["Branch moves"] --> S2["Changes stay staged"]
  end
  subgraph mixed["--mixed (default)"]
    M1["Branch moves"] --> M2["Changes stay in working tree, unstaged"]
  end
  subgraph hard["--hard"]
    H1["Branch moves"] --> H2["Working tree and staging match the target — changes discarded"]
  end

# Squash the last three local commits into one
git reset --soft HEAD~3
git commit -m "Add order retries with backoff and metrics"

# Make local main match the remote exactly, discarding local commits
git fetch
git reset --hard origin/main

Revert: Undo by Adding a Commit¶

git revert 9f3c2d1                     # new commit that reverses 9f3c2d1
git revert --no-edit HEAD~2..HEAD      # revert the last two commits, one revert commit each
git push

Reverting a merge commit needs to know which parent is the mainline:

git revert -m 1 <merge-sha>            # keep parent 1 (main), undo what the merged branch brought in

On a squash-merge workflow, each pull request is one commit, so git revert <sha> cleanly undoes one whole change — often the fastest production rollback.

The Reflog: Git's Safety Net¶

Every time a branch or HEAD moves — commit, reset, rebase, checkout — Git records it in the reflog. Commits you "lost" are usually still there.

$ git reflog
e44a7b1 (HEAD -> feature/retry) HEAD@{0}: reset: moving to HEAD~2
91c0d3e HEAD@{1}: commit: Add retry metrics
7ab21f4 HEAD@{2}: commit: Retry on 503
b7e41c9 HEAD@{3}: checkout: moving from main to feature/retry

Recover after a bad reset --hard¶

git reset --hard HEAD@{1}              # move back to where you were before the reset
# or keep the recovered work on a new branch
git branch recovered 91c0d3e

Recover a deleted branch¶

git reflog | grep 'feature/search'     # find the last commit it pointed to
git branch feature/search <sha>

Recover after a rebase went wrong¶

git reflog                             # find the entry before "rebase (start)"
git reset --hard HEAD@{5}

Reflog entries are local to your clone and expire (by default, reachable entries after 90 days and unreachable ones after 30). Recover promptly, and remember that a teammate's reflog can't rescue your work.

Cherry-Pick¶

Copy a commit onto the current branch as a new commit:

git switch release/2.4
git cherry-pick -x 9f3c2d1             # -x appends "(cherry picked from commit ...)"
git cherry-pick -x a1b2c3d..f6e5d4c    # a range (excludes the first commit)
git cherry-pick --abort                # if conflicts get out of hand

Use it for backporting fixes. If you cherry-pick often between long-lived branches, that's a sign your branching strategy needs attention.

Stash¶

Park uncommitted work to switch context:

git stash push -m "half-done retry config"
git stash push --include-untracked -m "with new files"
git stash list
git stash show -p stash@{0}
git stash pop                          # reapply and drop
git stash apply stash@{1}              # reapply and keep
git stash drop stash@{1}

Stashes are easy to forget. For anything that lasts longer than a few minutes, commit to a branch instead.

Bisect: Find the Commit That Broke It¶

Binary search through history. With 1,000 commits between good and bad, it takes about 10 steps.

git bisect start
git bisect bad                          # the current commit is broken
git bisect good v2.3.0                  # this release worked
# Git checks out a commit halfway; test it, then mark it:
git bisect good    # or: git bisect bad
# ...repeat until Git prints "<sha> is the first bad commit"
git bisect reset

Automate it with a script that exits 0 for good and non-zero for bad:

git bisect start HEAD v2.3.0
git bisect run ./scripts/test-checkout-flow.sh
git bisect reset

Worktrees: Two Branches at Once¶

Instead of stashing to review a hotfix, check out another branch in a separate directory:

git worktree add ../app-hotfix hotfix/payment-timeout
cd ../app-hotfix
# ...work, test, commit, push...
cd - && git worktree remove ../app-hotfix

Common Mistakes¶

• git reset --hard on a branch others have pulled, then force-pushing — use git revert instead.
• Running git clean -fd or git restore . without previewing, and deleting uncommitted work permanently.
• Panicking after a bad rebase instead of checking git reflog.
• Re-merging a branch after reverting it, and being surprised nothing comes back.
• Leaving important work in a stash for weeks.
• Cherry-picking fixes to a release branch but never to main.

Interview Questions¶

• What's the difference between git reset and git revert? When must you use revert?
• Explain --soft, --mixed, and --hard for git reset.
• You ran git reset --hard and lost two commits. How do you get them back?
• How do you undo a merge commit that's already on main?
• How would you find which of the last 500 commits introduced a bug?

Next¶

Continue to Collaboration and Repository Hygiene.