Hyperref + \url: long URL with dashes won't break

Load the url package explicitly with the hyphens option:

\usepackage[hyphens]{url}
\usepackage{hyperref}

By default, the url package does not consider hyphens as legal break points.

The above answer by mhp may not provide a solution when PDFLaTeX complains with "Option clash for package url."

The cause of this may be because of the package hyperref, which also loads the package. If hyperref is loaded before the url package it gives this error, because the url package is then loaded twice with different options: one without and one with hyphens option (this always causes a clash).

If you must load url after hyperref, you can first specify the hyphens option with the PassOptionsToPackage command:

\PassOptionsToPackage{hyphens}{url}
\usepackage{hyperref}
\usepackage{url}

Note that you do not need to provide the hyphens option a second time when loading the url package (or load url explicitly at all).

I noticed that the biblatex package apparently also clashes with url. Therefore, the same goes for biblatex as for hyperref: load url before it or use PassOptionsToPackage.

To moewe and Heilo; I know, I'm sorry and I would have, but as you said, I cannot make comments until a I have a certain 'reputation'. So I will edit my 'answer' to turn it into a real answer. Maybe I shall now collect enough reputation ;-)

Strange, my other post is deleted, and it still advised me to edit that one rather than making a new one! (It also was still visible, in red!)