Undo & Recovery

• Every undo command targets one or more of these areas
• Pick the area first, then pick the command

• git status shows which area holds the change
• git log --oneline -5 shows the latest commits
• Run both before any undo

• --source takes any commit: HEAD~2, a branch, a tag
• -p asks per hunk: y discard, n keep, s split
• Other hunks in the file stay untouched

git restore --source=HEAD~2 app.py
git restore --source=HEAD~2 --staged --worktree app.py
git restore -p app.py

old content into worktree; into both; chosen hunks only

• git reset <commit> moves the current branch pointer to that commit
• The mode decides what else is rewound: index, working tree

• --soft HEAD~1 undoes the last commit, files stay staged
• Ideal for redoing or squashing the last commits
• HEAD~3 goes back three commits

git reset --soft HEAD~1   # keep staged
git reset HEAD~3          # mixed: unstaged

soft keeps the index; mixed drops it

• --hard discards uncommitted edits, so run git status first
• ORIG_HEAD records the previous tip, so it undoes a bad merge or reset

git reset --hard ORIG_HEAD

back to the tip before the merge or reset

• git commit --amend replaces the last commit
• Fix its message, or stage more files and add them without a new commit
• --no-edit keeps the message and adds the newly staged changes

git add forgotten.txt
git commit --amend --no-edit

adds the file, same message

• git revert <commit> adds a new commit that inverts those changes
• History stays intact, so it is safe on shared branches
• -m 1 selects the mainline parent (1 = the branch you merged into)
• A..B reverts a range of commits
• -n stages the reverts without committing, so they fold into one commit

git revert <commit>
git revert -m 1 <merge-commit>
git revert -n A..B
git commit -m "revert A..B"

single, merge, then a range as one commit

• git reflog lists where HEAD (and each branch) pointed over time
• Entries look like HEAD@{2}: two moves ago
• Local only: never pushed to a remote

• git branch -D deletes the label only
• Commits remain until gc, so recovery is quick

git branch -D feature
git reflog                   # find its last hash
git branch feature a1b2c3d   # label is back

recreate a deleted branch

• Reachable entries expire after 90 days
• Unreachable entries expire after 30 days

• Shared branch: git revert <hash>, then a normal git push
• No force needed: history only grows
• Rewriting your own pushed branch: --force-with-lease, it refuses if the remote has new commits

• Never reset or amend on main or any branch teammates pulled
• Never bare --force: it overwrites blind

git revert <hash>
git push
git push --force-with-lease

revert for shared, lease only for your own branch