The fix_data.yaml file in flutter/flutter is growing, it is (at time of writing) about 4000 lines long.
I am looking into writing rules to migrate to the new button universe, and I expect these rules will be many many lines themselves.

It would be nice if I could break up the fix_data.yaml file into multiple files.

They could be organized by library, or in the case I am working on now, I might like to just have one for buttons since it is expected to be substantial. Maybe the top-level fix_data.yaml can coalesce multiple .yaml fix files from a subdirectory called fix_data.