UTF-8 mac file names problem
Man page convmv:
Linux and (most?) other Unix-like operating systems use the so called normalization form C (NFC) for its UTF-8 encoding by default but do not enforce this. Darwin, the base of the Macintosh OS enforces normalization form D (NFD), where a few characters are encoded in a different way. On OS X it's not possible to create NFC UTF-8 filenames because this is prevented at filesystem layer. On HFS+ filenames are internally stored in UTF-16 and when converted back to UTF-8, for the underlying BSD system to be handable, NFD is created.
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I think it was a very bad idea and breaks many things under OS X which expect a normal POSIX conforming system. Anywhere else convmv is able to convert files from NFC to NFD or vice versa which makes interoperability with such systems a lot easier.