Currently, when two parts in the same snapcraft.yaml file attempt to stage the same file at the same location, it's an error only if the files have different contents. I think this is dangerous -- at the very least, even if two conflicting files have the same contents, this should generate a warning, if not an outright error. It's unwise to depend on the unpredictability of the contents of two files, which might be identical for months, only to suddenly differ and start throwing build errors.