I am using
It seems you want to change the author name for all the commit histories. You can use
git filter-branch to change the author name:
git filter-branch --commit-filter ' if [ "$GIT_AUTHOR_NAME" = "old name" ]; then GIT_AUTHOR_NAME="new name"; git commit-tree "$@"; else git commit-tree "$@"; fi' HEAD
It will take a few minutes to rewrite the commit history.
After that you can use
git push -f --all to update the remote repo.