Hi there! the udev-rules file for mdadm in udev-repository was updated (see URL). I think it is worth to use this for mdadm ebuild.
feel free to update the mdadm package that said, why isnt the file just being included with udev itself ?
This is just following upstream. I have no problem letting sys-fs/udev provide the file. I guess upstream does it that way, because it is included in mdadm package for many distros. We should be able to change this using (maybe new style, EAPI2) blockers between updated udev containing the rules and older mdadm also containing them.
Added in 2.6.9.