modify-git-author.sh

#!/bin/sh

git filter-branch --env-filter '

an="$GIT_AUTHOR_NAME"
am="$GIT_AUTHOR_EMAIL"
cn="$GIT_COMMITTER_NAME"
cm="$GIT_COMMITTER_EMAIL"

if [ "$GIT_COMMITTER_EMAIL" = "[Your Old Email]" ]
then
    cn="[Your New Author Name]"
    cm="[Your New Email]"
fi
if [ "$GIT_AUTHOR_EMAIL" = "[Your Old Email]" ]
then
    an="[Your New Author Name]"
    am="[Your New Email]"
fi

export GIT_AUTHOR_NAME="$an"
export GIT_AUTHOR_EMAIL="$am"
export GIT_COMMITTER_NAME="$cn"
export GIT_COMMITTER_EMAIL="$cm"
'