From Fedora Project Wiki
mimeinfo
Use this when a package drops an XML file in %{_datadir}/mime/packages.
%post
touch --no-create %{_datadir}/mime/packages ||:
%postun
if [ $1 -eq 0 ] ; then
touch --no-create %{_datadir}/mime/packages ||:
/usr/bin/update-mime-database %{_datadir}/mime --somenewoption &> /dev/null || :
fi
%posttrans
/usr/bin/update-mime-database %{_datadir}/mime --somenewoption &> /dev/null || :
Note that similarly to the gtk-update-icon-cache code, these scriptlets should be run only if the user has update-mime-info installed and without a specific Requires: shared-mime-info. If shared-mime-info is not installed, update-mime-database won't be run when this package is installed. This does not matter because it will be run when the shared-mime-info package is installed.