apple this is exactly backwards
https://github.com/apple-oss-distributions/patch_cmds/blob/5084833f90df1b0e0924ea56f94c0199b3b8bbc6/diff/diffreg.c#L1800-L1808
https://pubs.opengroup.org/onlinepubs/9699919799/utilities/diff.html#tag_20_34_10_07
somebody at apple please inform them that `COMMAND_MODE=legacy diff` is in fact the UNIX‐compliant diff and always has been
A small, community‐oriented Mastodon‐compatible Fediverse (GlitchSoc) instance managed as a joint venture between the cat and KIBI families.
Lady, EVOLVED 
somebody at apple please inform them that `COMMAND_MODE=legacy diff` is in fact the UNIX‐compliant diff and always has been