rg3/youtube-dl — pull request #3890 by xu-cheng (2014-10-06 11:07:28+00:00)
Title: Zsh Completion Support

ref: https://github.com/rg3/youtube-dl/issues/3814

I'm not expert on zsh programming. So it may not perfect. Also it's worth noted that the install part of homebrew formula should be updated accordingly.