Specifically:
- A data fork dump file will always exist
- A resource fork dump file will exist iff there are any bytes in that
fork (but this dump file may be empty)
- A Finder info dump will exist if there are any nonzero bytes in the
type or creator code
Filenames that MacOS sees as ending with .rdump or .idump are reserved
for resource fork and Finder info dumps. They are ignored on the HFS
side and complained about on the local side. This also applies to files
named underscore (_), which are reserved for directory Finder info.
Dotfiles are ignored on both sides (but warned about on the HFS side) to
make some modern tooling invisible to the MacOS.
Elliot Nunn