[Feature request] Add shell command completion autogeneration

[yermulnik]

fswitch already has around a dozen+ of command line arguments which is complicate to remember and operate by humans when necessary.
Would be great to look up and employ a Golang library to autogenerate shell command completions from code on the fly (e.g. tswitch --completion bash) that can be soaked into shell dynamically (e.g. . <(tfswitch --completion bash)).

Common shells that shell command completion is shipped for usually are: Bash, Zsh, Fish, PowerShell.

Once implemented, update documentation with manual steps and Homebrew formulae to autogenerate and install shell command completions into common location.
Caveat: only @warrensbox has write access to https://github.com/warrensbox/homebrew-tap

FWIW: https://github.com/spf13/cobra/blob/main/site/content/completions/_index.md

[yermulnik]

FWIW: until this is not implemented by means of tfswitch command

# shellcheck disable=SC2207 # W: Prefer mapfile or read -a to split command output (or quote to avoid splitting).
_tfswitch()
{
    local cur prev
    cur=${COMP_WORDS[COMP_CWORD]}
    prev=${COMP_WORDS[COMP_CWORD-1]}

    if [[ ${cur} == -* ]]; then
        COMPREPLY=( $( compgen -W "$( tfswitch --help 2>&1 | grep -Eo '[[:space:]]+(-{1,2}[a-zA-Z0-9-]+)')" -- "$cur" ) )
        return 0
    fi

    case "${prev}" in
        -A|--arch)
            COMPREPLY=( $( compgen -W "386 amd64 arm arm64" -- "$cur" ) )
            return 0
            ;;
        -b|--bin)
            _filedir
            return 0
            ;;
        -c|--chdir|-i|--install)
            _filedir -d
            return 0
            ;;
        -g|--log-level)
            COMPREPLY=( $( compgen -W "DEBUG ERROR INFO NOTICE TRACE" -- "$cur" ) )
            return 0
            ;;
        -t|--product)
            COMPREPLY=( $( compgen -W "opentofu terraform" -- "$cur" ) )
            return 0
            ;;
    esac

} &&
complete -F _tfswitch tfswitch

# vim: filetype=bash shiftwidth=4 tabstop=4 expandtab autoindent:

[yermulnik]

JFYI: #586