#1885 diffs not showing up for files not known to be displayable
We're kind of finicky about what files we'll try to display or not, and somehow this has carried over to our repo diffs. If the underlying file is not known to be displayable, we show the diff link, but it leads to a dead-end where you can download the file in question --- but not see the diff.
Probably we need to (a) rethink our ideas about what files are displayable; and (b) assume a diff is always displayable.
b)
Update is on js/1885
Looks good