[Git] Undoing Changes

#Reverting local changes

git checkout .

or

git restore .

Reverts all unstaged modifications under the current directory.
Untracked files are unaffected: files excluded by .gitignore, or newly created files.

#Undoing git add

git reset HEAD {file-name}

or

git reset {file-name}

or

git restore --staged {file-name}

Changes the files passed as arguments back to the unstaged state.

#Amending the most recent commit

git commit --amend

This is a command I personally use quite often.
It lets you add newly staged (git add) changes to the most recent commit, or edit the commit message.
If it needs to be reflected on a shared branch of origin, the force option (git push -f) is mandatory, and I'd recommend doing it only on feature branches you're working on alone, not on branches shared with colleagues.

#Undoing git commit

#Method 1: --soft

git reset --soft HEAD^ // 최근 커밋 1개 취소

Undoes the most recent commit and leaves the committed changes in the staged state.

#Method 2: --mixed

git reset HEAD^ // 최근 커밋 1개 취소

git reset HEAD~2  // 최근 커밋 2개 취소

git reset --mixed HEAD^

Undoes the most recent commit and leaves the committed changes in the unstaged state.
They get mixed with your local changes.

#Method 3: --hard

git reset --hard HEAD^

Undoes the most recent commit and discards the committed changes entirely.

#Undoing a commit on a remote branch

When you've committed to origin via git push but want to undo that commit.

git log --oneline
872fa7e Try something crazy <- 되돌리고 싶은 커밋
a1e8fb5 Make some important changes to hello.txt
435b61d Create hello.txt
9773e52 Initial import

Given a remote branch history like the above, suppose you want to revert commit 872fa7e.

git revert HEAD

git push

Adds a new commit to origin that reverts the most recent commit.

git log --oneline
e2f9a78 Revert "Try something crazy"
872fa7e Try something crazy
a1e8fb5 Make some important changes to hello.txt
435b61d Create hello.txt
9773e52 Initial import

After git push, origin ends up with a new commit as shown above.

Why you shouldn't use git reset

The git reset command erases a commit from git history as if it never happened.
If you erase a commit on a shared collaboration branch of the remote this way, it can be a huge nuisance for colleagues who were working based on that commit.

Therefore, use git reset only when all colleagues are aware of it; by default, git revert is recommended.