git filter-branch -f --env-filter '
if [ "$GIT_COMMITTER_NAME" = "oldname" ];
then
  GIT_COMMITTER_NAME="newname";
  GIT_COMMITTER_EMAIL="newemail";
  GIT_AUTHOR_NAME="newname";
  GIT_AUTHOR_EMAIL="newemail";
fi
if [ "$GIT_AUTHOR_NAME" = "oldname" ];
then
  GIT_COMMITTER_NAME="newname";
  GIT_COMMITTER_EMAIL="newemail";
  GIT_AUTHOR_NAME="newname";
  GIT_AUTHOR_EMAIL="newemail";
fi
'