I think this feature was sort of a mistake, where the ease of access to diff -bw shaped behavior a very long time ago and then the train just ran a long way down the tracks in the same direction.
Grepped for whitespace, deleted almost everything. Poked around the UI a bit. I'm expecting the whitespace changes to get some more iteration this week so I not being hugely pedantic about testing this stuff exhaustively.
See T13161. This is basically the piece I'm going to restore in the next diff to improve line alignment when lines changes only by changing whitespace, so this is coming back in some form soon.
This piece may need to come back, too.
This isn't really a generated file; it's just designed to appear as one, right? Presumably there isn't a very good way to actually test this stuff without also incidentally adding a "This is a generated file which doesn't need to be reviewed" message when reviewing revisions that touch these files.
Right, this is testing the rendering of generated files. We could work around this with some mangling in the test harness, but it's such a weird special case that it doesn't seem terribly valuable.