Clearly denote adapter interface for file reloading

[maclover7]

cc @tenderlove

Laying groundwork for #24981.

[matthewd]

Thanks, but this is a heavyweight adapter pattern for something that's just recently grown a second implementation, and I don't foresee a third.

[maclover7]

This was closed due to uncertain future about if/how @tenderlove's forking idea would be implemented, and if an adapter/plugin pattern would be used.