[Bug] Media Type-specific rendering changes cannot be previewed, when a file is renamed, but otherwise unmodified.

If a repository contains `ReadMe.txt`, which contains CommonMark markup, when renamed to `ReadMe.MD`, the modifier cannot preview the file without modifying it. Instead, it states:

> The file was renamed but not changed.

Luckily, adding whitespace is a trivial workaround. However, it should not be required. This may have made the issues, that [`/search?q=%22The+file+was+renamed+but+not+changed%22&type=issues`](https://github.com/search?q=%22The+file+was+renamed+but+not+changed%22&type=issues) returns, easier to diagnose.