Fancy web diffs are nice, and great because of their commenting features. However, getting notified just with abbreviated mails means less eyes on any given commit because the threshold for viewing the actual commit is higher. Being able to include the actual commit diffs has a number of benefits:
* I'll casually look at some the more important commits (or just some of the shorter, easy to read ones) that are going on in our project, and passively learn/observe other people's code.
* My boss can (and will) read commit diffs while he's on a plane, without internet access.
* There will be useful comments or fixes from people who weren't reviewers but ended up reading the commit diffs anyway.
* Including the commit diff means including the commit message, which is educational even for people who decide not to bother with the code this time around.
Ideally there would be a setting in the Herald commit notification email rule that lets the user specify how large of a commit diff should maximally be included in the mail, to avoid potential data volume issues but still get the gist of it. The email format could be the same as now, with diffs being (optionally) appended to the commit summary.