range-diff: diff links at the top do not show before/after diff #2529

For example, consider this. The two links at the top for the "old and new diff" link to

• https://github.com/rust-lang/miri/compare/3f73c6eaa7be1fe504d03a978c53aef22491b840..c8aa21db093296ac545e149556dc1da3dd9806a8
• https://github.com/rust-lang/miri/compare/c4ec4e636cbeac9b6ebca8a540a35aca985287aa..4dea1c37b0adc7927e1a2def6471cdd2b3828eb4

Neither of them looks anything like what the PR actually does. I think this should link to the triple-dot ... diff form, not the double-dot ...