I'm having trouble registering a new mime type. I had this working in Fedora 26 (and 27 iirc) but it seems to not be working in F28. I'm adding some lines to /usr/share/misc/magic and then recompiling and replacing /usr/share/mime/magic.mgc . In the past this has worked to patch the mime type this way and still works in RHEL/CentOS 7.  

Using 
file --mime-type -k  exampleFile.ica 
I can see my entry as the second item, but even after adding `!:strength +250` it doesn't override the default, which is application\x-wine-extension-ini 
 
I even went so far as to remove all lines containing x-wine-extension-ini from the magic file but the assignment persists, which makes me think that either file no longer looks to /usr/share/mime/magic.mgc for the only place for mime types, there's a bug, or something else I haven't considered. 

I'm happy to fill out a bug report (search through bugzilla I don't see anything) but didn't want to if there was just a change that I missed.