This way it's clearer to users that an argument is expected. It's
likely that this commit does not catch all such cases, but it should
do it for most of the affected commands I have installed.
Turn it on dynamically when needed instead; see doc/styleguide.txt for
a longer explanation. This fixes many non-filename completions which
had been previously more or less broken due to unwanted
escape-as-filenames behavior.
_usergroup now has a -u option, and there are new _allowed_users and
_allowed_groups helpers. These can be used to limit returned users
and/or groups to ones that the user has access to (or should be
assumed to have access to if running a "root command").
I had to remove a couple of "funky user" chown test cases because for
some reason they were broken by this change, I didn't immediately find
out why, and I couldn't come up with a valid use case that should be
supported for them that would be more beneficial than the relevance
improvements in this patch.
