Very strange. Perhaps it's some setup- or platform-dependent thing; I will file an issue. Thanks for checking!
EDIT: Very strange; I thought I'd give a try to what seemed a throwaway comment in your post, about quoting the string, and that fixed it. Thanks!
Without the double quotes (which seemed to be unnecessary for you), I still get:
$ youtube-dl https://www.youtube.com/watch?v=wbKJt1NQtZE
Usage: youtube-dl [OPTIONS] URL [URL...]
youtube-dl: error: You must provide at least one URL.
Type youtube-dl --help to see a list of all options.
I guess that some alias is grabbing some part of the URL string.
Interesting! It seems that my `echo` is eating any substrings involving `?`.
$ bash --version
GNU bash, version 4.3.42(1)-release (x86_64-apple-darwin13.4.0)
Copyright (C) 2013 Free Software Foundation, Inc.
License GPLv3+: GNU GPL version 3 or later <http://gnu.org/licenses/gpl.html>
This is free software; you are free to change and redistribute it.
There is NO WARRANTY, to the extent permitted by law.
$ echo a ? = =?
a =
EDIT: Very strange; I thought I'd give a try to what seemed a throwaway comment in your post, about quoting the string, and that fixed it. Thanks!
Without the double quotes (which seemed to be unnecessary for you), I still get:
I guess that some alias is grabbing some part of the URL string.