Adds a --quiet/-q option for command -s

[floam]

Description

I think devnull'ing command -v program_name to check presence is a common
enough chore that a --quiet option which works like it does on type would be handy for writers of shell scripts. Simply mutes the output for checking the exit status.

command -qs foo should behave identically to command -s foo >/dev/null, command -v foo >/dev/null

Includes updated documentation.

[faho]

As I read this, this still accepts "-q" without "-s" as a noop.

Personally, I'm okay with that, but there might be reasons to error out - I think @krader1961 likes behavior like that.

[floam]

As I read this, this still accepts "-q" without "-s" as a noop.

No, that's an error and the help is printed.

edit: oops, I hit the close pull request instead of the green comment button.

[floam]

(command -q is an error, command -q commandname is also an error. )

This function here only does the argument handling aspect of the builtin, outside the parser, and it already was causing errors unless print_path is true.

[franciscolourenco]

How does this compare to type -q?

[krader1961]

How does this compare to type -q?

Using command -qs some_command is more natural when you want to explicitly test if an external command (i.e., program) exists by that name in $PATH. Using type -q is appropriate if you just want to verify that a command of the given name exists whether it's a builtin, function, or external command.