Add custom subcommand into any command

with-subcommand.zsh

#!/bin/zsh
#
# with-subcommand.zsh
#
# Description:
#
# Add custom subcomand into any command
#
# Installation:
#
# $ git clone https://github.com/yosugi/with-subcommand.zsh
# $ cp with-subcommand.zsh/with-subcommand.zsh ~/.with-subcommand.zsh
# $ echo '[ -f ~/.with-subcommand.zsh ] && source ~/.with-subcommand.zsh' >> ~/.zshrc
# $ source ~/.zshrc
#
# Usage:
#
# * install & load with-subcommand.zsh
# * define subcommand in .zshrc
#     * if you want to add `tmux args` command, define `tmux-args` function, alias, or command.
#     * see below example
#
# Example:
#
# If you want to add `tmux args` subcommand,
# Write below script your .zshrc
#
# ```
# [ -f ~/.with-subcommand.zsh ] && source ~/.with-subcommand.zsh
# alias tmux='(){ with-subcommand tmux "$@" }'
# function tmux-args() {
#     echo "args:" "$@"
# }
# ```
#
# You can use tmux subcommand "tmux args".
#
# ```
# $ tmux args 1 2 3
kj# args: 1 2 3
# ```
#
# You can use original tmux subcomannd too.
#
# ```
# $ tmux ls
# develop: 4 windows (created Thu Mar 21 18:35:49 2018) [136x65] (attached)
# ```
#
# Version: 0.1.0
# Author : yosugi
# License: MIT

function with-subcommand() {
    local args
    local subcommand
    subcommand="$1-$2"

    if type "$subcommand" >/dev/null 2>&1; then
        args=("${@:3}")
        eval "$subcommand" "${args[*]}"
        return $?
    fi

    args=("${@:2}")
    eval \\"$1" "$args[*]"
    return $?
}

# example
# alias tmux='(){ with-subcommand tmux "$@" }'
# function tmux-args() {
#     echo "args:" "$@"
# }