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.
