change author in git history

# for the latest commit

$ git commit --amend --no-edit --reset-author

# for the whole project

$ git rebase -r --root --exec "git commit --amend --no-edit --reset-author"

# in one go

$ if [ "$GIT_AUTHOR_EMAIL" = "<old-email>" ];
GIT_AUTHOR_EMAIL="<new-email>";
git rebase -r <some commit before all of your bad commits> \
--exec 'git commit --amend --no-edit --reset-author'