If a developer (or CI) gets a review request to review he
will get a whole URL because it was copy+pasted from browser.
This change allows to easily use that URL to get the patch
of given review request.

Provided an URL to rbt patch and saw that it extract the

review_request_id and the diff_id correctly and saw that

it correctly used the host.
Also provided an URL as interdiff format /4-5/ and

saw it was refused.