The commit that incorrectly refactored e-mail templtes to use

build_server_url() over {{domain_method}}://{{domain}} in the e-mail

templates regressed behaviour in the diff fragment template. It did not

actually pass the new site_url context variable to the template. 

Additionally, we weren't actually using the context passed to

build_diff_comment_fragments to render the template.
Both issues are now resolved, resulting in correctly-rendered templates.

Viewed review and review reply preview e-mail views and saw absolute

links.