When opening a pull request that renamed a CSV file:
the compare page fails with a 500.
Fix: load the left blob for every file that was not added, and the right blob
(from `Name`) for every file that was not deleted. That matches what the
templates did before #38517.
Co-authored-by: Claude Opus 5.5 <noreply@anthropic.com>
Co-authored-by: wxiaoguang <wxiaoguang@gmail.com>