I accidentally typed `brew update --greedy` instead of `brew upgrade --greedy` and got some strange output.
This fix causes unrecognized long options to throw a usage message and exit like all the other subcommands.
Before:
```
% brew update --greedy
==> Updating Homebrew...
Usage: brew update-report [--auto-update] [--force]
The Ruby implementation of brew update. Never called manually.
[...]
```
After:
```
% brew update --greedy
Error: Unrecognized option '--greedy'
Usage: brew update, up [options]
Fetch the newest version of Homebrew and all formulae from GitHub using git(1)
and perform any necessary migrations.
[...]
```
85c9551cd3