Re: [PATCH v4 1/5] refs: introduce `is_pseudoref()` and `is_headref()`

Patrick Steinhardt [off-list ref] writes:

I think it's quite confusing that `is_pseudoref()` not only checks
whether the refname may be a pseudoref, but also whether it actually
exists. Furthermore, why is a pseudoref only considered to exist in case
it's not a symbolic ref? That sounds overly restrictive to me.

I am torn on this, but in favor of the proposed naming, primarily
because is_pseudoref_syntax() was about "does this string look like
the fullref a pseudoref would have?", and the reason why we wanted
to have this new function was we wanted to ask "does this string
name a valid pseudoref?"

 Q: Is CHERRY_PICK_HEAD a pseudoref?
 A: It would have been if it existed, but I see only
    $GIT_DIR/CHERRY_PICK_HEAD that is a symbolic link, and it cannot
    be a pseudoref.

I can certainly see a broken out set of helper functions to check

 - Does this string make a good fullref for a pseudoref?
 - Does a pseudoref with his string as its fullref exist?

independently.  The first one would answer Yes and the second one
would answer No in such a context.

Thanks.