fix: zsh autocompletions

[mahyarmirrashed]

Actually auto-complete.

For some reason, the auto-completion wasn't working for me. Running <prog> -- --generate-shell-completion just ran the command, and did not provide the correct results. The reason that was happening (if I had to guess) is because -- is being treated as an end of flags. As such, the literal string --generate-shell-completion was being passed to the underlying program.

What type of PR is this?

• bug

What this PR does / why we need it:

Current completions do not work for ZSH. I spent 3 hours trying to figure out what it was.

Which issue(s) this PR fixes:

Partially fixes #2173

Release Notes

fix: zsh autocompletions

[mahyarmirrashed]

Admittedly, this is just a patch over the old problem. There probably needs to be actual source code changes to make it work properly.

e.g.

mahyar@tiger tmp % ./greet add - --generate-shell-completion
--config:path to config file
--help:show help
mahyar@tiger tmp % ./greet add --conf --generate-shell-completion
help:Shows a list of commands or help for one command