I think that the autocomplete story is abysmal. Modern IDEs can tell me exactly what can follow after a certain piece of text, and even the best tab completion in terminals is limited, ugly, and text-mode for no good reason.

Some protocol for a real dropdown rendered in the style of the OS, plus a standard data format that allows tool builders to specify options, their meanings and the kinds of allowed parameters in a structural way (much like doccomments in code), is direly needed.

If I type "git " I want to see "add" as an option, with docs in a tooltip as I navigate the options. When I "git add " I want to see a list of files that make sense to add, eg only files that can be staged right now.

I want this to be consistent across commands, I want any shell to be able to add support for this and I want any command line program to be able to add support for this.

This. I would love to be able to type "[command] --[tab]" and have it list all the options, and/or common options, so when I'm learning 'tar' I don't have to start typing, realize I've forgotten the command, and then have to go use man or --help or go Google it.

Have you checked out ZSH? It can do this nicely.

zsh via its ultra-tunable completions can do only 1st part of op's request i.e command option completion, but not the second part i think...

for example, i do the following:

    anupam@virat ~ % autoload -Uz compinit
    anupam@virat ~ % compinit
    anupam@virat ~ % git a
    add        -- add file contents to index
    am         -- apply patches from a mailbox
    apply      -- apply patch to files and/or to index
    archimport -- import an Arch repository into git
    archive    -- create archive of files from named tree

Edit: looks like it might be stock behaviour https://github.com/zsh-users/zsh/blob/master/Completion/Unix...