Let's you do a forceful rewrite of the git history swapping orphaned authors.

author-rewrite-commit-history-git.sh

# ex: ./author-rewrite-commit-history-git.sh "dannygershman@cinchcast.com" "Danny Gershman" "danny.gershman@gmail.com$

oldname=$1
newname=$2
newemail=$3

git filter-branch -f --commit-filter '
        if [ "$GIT_COMMITTER_NAME" = "'$oldname'" ];
        then
                GIT_COMMITTER_NAME="'"$newname"'";
                GIT_AUTHOR_NAME="'"$newname"'";
                GIT_COMMITTER_EMAIL="'"$newemail"'";
                GIT_AUTHOR_EMAIL="'"$newemail"'";
                git commit-tree "$@";
        else
                git commit-tree "$@";
        fi' HEAD

git push --force