all branches and tags:
git filter-branch --env-filter 'GIT_AUTHOR_EMAIL=<author mail adress> GIT_COMMITTER_EMAIL=<committer mail adress>' -- --all
last three commits
git filter-branch --env-filter 'GIT_AUTHOR_EMAIL=<author mail adress> GIT_COMMITTER_EMAIL=<committer mail adress>' HEAD~3..HEAD