Should "head" also work for "HEAD" on case-insensitive FS?

I don't have a OSX box, but was helping a co-worker over Jabber the other day, and he pasted something like:

    $ git merge-base github/master head

Which didn't work for me, and I thought he had a local "head" branch until realizing that of course we were just resolving HEAD on the FS.

Has this come up before? I think it makes sense to warn/error about these magic /HEAD/ revisions if they're not upper-case.

This is likely unintentional and purely some emergent effect of how it's implemented, and leads to unportable git invocations.