scripts: Zsh completion should work with subcommands

[ghost]

For example: dvc metrics show <tab>.

The way to support this would be to modify the way we parse our arguments to support subcommands

dvc/scripts/completion/dvc.zsh

Lines 231 to 240 in dd8598e

	$_dvc_options \
	'1: :_dvc_commands' \
	'*::args:->args'
	case $words[1] in
	init) _arguments $_dvc_global_options $_dvc_init ;;
	destroy) _arguments $_dvc_global_options $_dvc_destroy ;;
	add) _arguments $_dvc_global_options $_dvc_add ;;
	import) _arguments $_dvc_global_options $_dvc_import ;;
	checkout) _arguments $_dvc_global_options $_dvc_checkout ;;

[jorgeorpinel]

I just want to add that specifically for dvc cache dir not all the $_dvc_global_options exist (-q, and -v specifically), while for all the other subcommands I think they do. Something to consider. (Maybe they should be added to the subcommand?)

[efiop]

@jorgeorpinel Good catch! Indeed, we've missed those there. Looks like we just need to use parents=[parent_parser, parent_config_parser] in https://github.com/iterative/dvc/blob/master/dvc/command/cache.py#L46 .

[casperdcl]

also see https://stackoverflow.com/questions/9000698/completion-when-program-has-sub-commands

[efiop]

Fixed in https://github.com/iterative/shtab