## Make sure your local repo settings are correct
git config --local --list
git config --local user.name "author name"
git confit --local user.email "name@example.com"

## Change previous n commits
git rebase -i HEAD~n
# choose the commits to change by adding 'pick' or 'reword' (only for changing the message)
git commit --amend --author="Author Name <email@address.com>"

## Change all commits with --commit-filter. If your local config was wrong
git filter-branch --commit-filter 'if [ "$GIT_AUTHOR_NAME" = "your previous name" ];
  then export GIT_AUTHOR_NAME="your New Name"; export GIT_AUTHOR_EMAIL=new.email@example.com;
  export GIT_COMMITTER_NAME="your New Name"; export GIT_COMMITTER_EMAIL=new.email@example.com
  fi; git commit-tree "$@"'