Autocomplete, or autosuggest, is a common feature for many command-line applications. Most command-line users are familiar with autocomplete when they type part of a command and press
tabto complete the rest of the command, or
tab-tabto see a list of commands matching that prefix.
Beyond autocomplete of the command name itself, there are ways to autocomplete sub-commands and/or options and arguments. As support for autocomplete often depends on external applications, and/or the terminal application you are using, autocomplete is a varied topic.
Cement does not currently have any mechanisms to support autocomplete out of the box. This document will serve as a helper for known ways you might find suitable for your needs.
Fig is "The next-generation command line" (per their site), with a suit of products that includes IDE-Style Autocomplete for 500+ CLI tools.
video from their site
Fig has built a Cement Extension that can be installed via PyPi, and included in your applications that are Built on Cement™.
Provides "Fish-like fast/unobtrusive autosuggestions for zsh".
BASH has mechanisms for implementing "Programmable Completion".