feature request: add standard "oci completions <shell>" command

[alexanderankin]

I have provided a sample implementation here: #917

[alexanderankin]

workaround:

. <(find "$(. ~/.oci-cli-venv/bin/activate; python -c 'import oci_cli; print(oci_cli.__path__[0])')" -name oci_autocomplete.sh -exec cat {} \;)