I presume 'root directory' mean the repository directory.

I would have to think about supporting this in IDLE.  It already, I believe (or will), enforces the two whitespace rules when saving and defaults to 4-space indents for first lines of statements.  Enforcing that for repository .py and .c files would be good, but there is currently no mechanism for per-file settings.

I did not see anything in the EditorConfig guide about what happens when .editorconfig does not start with root = true and another file is found.