Since this appears to just be a wrapper around the existing aws cli, I believe the command you are looking for is `s3 cp <local directory or file> s3://<full s3 bucket url> --recursive`. Just an educated guess taken from the CLI docs: https://aws.amazon.com/cli
You can do that through the regular AWS cli tools with "aws s3 cp..." or with external tools like s3cmd which is a third party s3 cli client.
In fact, this even can even sync new/modified/deleted files, similar to rsync. Very handy for deploying static assets or backups, for example.
aws s3 sync --delete [--acl public-read] ...
We've been using rclone[1] at work for automatically archiving builds from CI and other useful things, it supports S3 and other services as well.