[tex-live] Possibility to have a package in two or more collections

[Karl Berry]

    is it possible for a package to be included in more than one collections?

No.  It's fundamental in TL that the collections exactly partition the
packages -- nothing left out, nothing duplicated.

    I think `polyglossia` shoudl be both in the `collection-xetex` and
    in the `collection-luatex` collection.

I agree something should be done.  There are a number of packages which
attempt to support both xetex and luatex; fontspec and unicode-math are
two others (right now in two other collection-*'s, for no particularly
good reason).

I have had thoughts of creating something like collection-unicodetex
(hopefully with a better name) with such packages, but have not done it
yet.  I think your email will spur me to do so :).

Best,
Karl