Bash completion in Vim commandline

[Enan Ajmain]

I use bang commands quite often, and sometimes I really miss the bash
completion for long arguments. I know I can add custom completion
entries for Vim user-defined commands, but that would get tedious for
someone who uses a lot of tools. Any way to add bash completions to Vim
commands?

Apart from using ":!cmd --arg=val", I use ":grep" quite a lot. I used
to use ripgrep which has short arguments so it's easy to type. But I
have switched to GNU grep and some of its arguments are quite long, eg,
"--exclude" and "--exclude-dir". Any way to complete arguments for Vim
commands that underneath calls external tools?

Enan