Hi - I'm curious if you'd be interested in adding a code type of "epub" for repositories. It's very similar to html/css, but is a particular file structure where a bunch of html, css, and xml files are zipped up into a package. I'm a small publisher (bitingduckpress.com) and we're finding that version control for epubs during book development and editing is tricky.
I'm mostly on the technical side of things, and am trying to move the word-side of things to using git. We're just starting to do git version control using html/css (what all the epubs start out as) but it would be a nice feature to be able to stick an epub in a repo and track changes to the individual files. It's probably not a big market for you right now, but it's got the potential for growth, as epub workflow and version control is pretty primitive right now. A lot of people use Adobe Indesign, which is actually much harder than working in a text editor and gives worse results (worse looking epubs with basic features missing). We typically are working on 5-10 titles at a time, with 3-4 people passing around edits. It's the kind of thing that I'd eventually put together for myself, but have my hands full with the rest of building/maintaining the web store and running the business. It's probably mostly a change to your source browser, so I'm flagging it there.
Thanks for at least reading this, and for offering a nice online service.