followup #406: diff all the plaintext things #483
Description
ref #406 (comment)
#406 has been reviewed/approved, and once it's pulled in we'll be able to diff plaintext files. However, the UI/frontend only allows diffing a file if its extension is recognized. Ideally, we should be able to diff any plaintext-like file that git diff can handle.
One approach would be to allow the user to ask for a diff of any file on the frontend (via the right click menu or otherwise) and then sort out diff-able files from binary files on the backend. On the backend, we can detect binary (and therefore not diff-able) files either via git (its a bit tricky to get git to cough up that particular piece of info, but apparently it's doable), or by using the same byte checking trick that git itself uses