These can't be resolved in the UI because if they aren't in a UTF-8
compatible encoding, they can't be rendered as JSON. Even if they could,
we would be implicitly changing the file encoding anyway, which seems
like a bad idea.
- Add match line header to expected result for `File#sections`.
- Lowercase CSS colours.
- Remove unused `diff_refs` keyword argument.
- Rename `parent` -> `parent_file`, to be more explicit.
- Skip an iteration when highlighting.