RFR: Make webrev reject positional arguments

[Leo Korinth via github.com]

The pull request has been updated with additional changes.

----------------

Added commits:
 - 372c4e95:	Update '--help' text to be consistant with man pages after review

Pull request:
https://git.openjdk.java.net/skara/pull/79

Webrevs:
 - full: https://webrevs.openjdk.java.net/skara/79/webrev.02
 - inc: https://webrevs.openjdk.java.net/skara/79/webrev.01-02

Updated full patch:
https://git.openjdk.java.net/skara/pull/79.diff

Fetch command:
git fetch https://git.openjdk.java.net/skara pull/79/head:pull/79