Jeff King [off-list ref] writes:
If you have a static list of attributes, that is OK (though you are
presumably better off with /etc/gitattributes or similar that covers all
repos).
...
but still tell users that "json" is a well-known name, and if they want
to get the same treatment for an arbitrary file "foo" that they would
get for "foo.json", they have to add attributes mapping it, like:
foo diff=json
inside their repo.
Yes, you described the reason very well why we didn't add "global"
or "system-wide" attribute files.
Thanks for commenting on my somewhat tongue-in-cheek "devil's
advocate" remark.