gistfile1.sh

NAME="foo"
EMAIL="foo@example.com"

git filter-branch -f --env-filter '
if [ "$GIT_AUTHOR_EMAIL" = "XXX" ];
then
  export GIT_AUTHOR_NAME=$NAME
  export GIT_AUTHOR_EMAIL=$EMAIL
  export GIT_COMMITTER_NAME=$NAME
  export GIT_COMMITTER_EMAIL=$EMAIL
fi'