(original title: For Email links have a way to specify the root URL instead of echoing what the user that triggered the email used)
Some systems can be reached by multiple URLs. For example on a windows domain using the machine name without a domain or with a domain. (E.g. http://kallithea/ vs http://kallithea.mycompany.com/)
However, not all users that receive an email with links will be able to access the repo from the same URL that was used to trigger the email. E.g. from a machine on my domain I could use http://kallithea/ but someone getting the email may not be on my domain and would need to use the full machine name + domain name, http://kallithea.mydomain.local/ . The fully-qualified URL works in both contexts, so I would prefer it to be used in emails even if I happened to type the shorter address into my browser.
Have a mechanism to specify the canonical root URL.