git-reauthor

#!/usr/bin/env bash

git filter-branch --env-filter '

old_author_email="$1"
new_author_name="$2"
new_author_email="$3"

if [ "$GIT_COMMITTER_EMAIL" = "$old_author_email" ]
then
    export GIT_COMMITTER_NAME="$new_author_name"
    export GIT_COMMITTER_EMAIL="$new_author_email"
fi
if [ "$GIT_AUTHOR_EMAIL" = "$old_author_email" ]
then
    export GIT_AUTHOR_NAME="$new_author_name"
    export GIT_AUTHOR_EMAIL="$new_author_email"
fi
' --tag-name-filter cat -- --branches --tags