To undo your last commit, use
git reset --soft HEAD~1
Change 1 to the number of commits. To undo the last 3 commits, use git rest --soft HEAD~3.
This git command does not cause any data loss, it only "un-commits" commits.
Example
Have you ever made multiple commits because you forgot to small typo or mistake?
git log --oneline
7b2cd48 (HEAD -> main) Update README again
047ecab Update README 2
dad0bf5 Update README typo
4a0bff2 Update README
71e5549 Initialize boilerplate
1fac9d8 First commit
Usually, you'd use git rebase for things like this. However, the commits we want to merge are the latest commits, so it is easier to undo them, then redo them as one commit.
We need to "un-commit" the last 4 commits, so use
git reset --soft HEAD~4
The last 4 commits are now undone:
git log --oneline
71e5549 (HEAD -> main) Initialize boilerplate
1fac9d8 First commit
Now add your new commit:
git commit -m "Update README"
And you've successfully rewritten history
git log --oneline
4f914d4 (HEAD -> main) Update README
71e5549 Initialize boilerplate
1fac9d8 First commit