Change the username and email of all commits that match the value of OLD_EMAIL var.

change-committer.sh

#!/bin/sh

git filter-branch --env-filter '

OLD_EMAIL="put old email here"
CORRECT_NAME="put new name here"
CORRECT_EMAIL="put new email here"

if [ "$GIT_COMMITTER_EMAIL" = "$OLD_EMAIL" ]
then
    export GIT_COMMITTER_NAME="$CORRECT_NAME"
    export GIT_COMMITTER_EMAIL="$CORRECT_EMAIL"
fi
if [ "$GIT_AUTHOR_EMAIL" = "$OLD_EMAIL" ]
then
    export GIT_AUTHOR_NAME="$CORRECT_NAME"
    export GIT_AUTHOR_EMAIL="$CORRECT_EMAIL"
fi
' --tag-name-filter cat -- --branches --tags