The complete command is inherited from the python-cliff library, it can be used to generate a bash-completion script. Currently, the command will generate a script for bash versions 3 or 4. The bash-completion script is printed directly to standard out.
Typical usage for this command is:
openstack complete | sudo tee /etc/bash_completion.d/osc.bash_completion > /dev/null
If installing python-openstackclient from a package (apt-get or yum), then this command will likely be run for you.