* rollback merge

```
# git reset --hard commit_sha
```

see [Undo a Git merge that hasn't been pushed yet](http://stackoverflow.com/questions/2389361/undo-a-git-merge-that-hasnt-been-pushed-yet).


* change commit authore

```
git commit --amend --author="Author Name <email@address.com>"
```

see [Change commit author at one specific commit](http://stackoverflow.com/questions/3042437/change-commit-author-at-one-specific-commit)