In most commands we load config before parsing command line
options, since it lets the latter override the former with a
simple variable assignment. In the case of for-each-ref,
though, we do it in the reverse order. This is OK with
the current code, since there's no interaction between the
config and command-line options.

However, as the ref-filter code starts to care about config
during verify_ref_format(), we'll want to make sure the
config is loaded. Let's bump the config to the usual spot
near the top of the function.

We can drop the comment there; it's impossible to keep a
"why we load the config" comment like this up to date with
every config option we might be interested in. And indeed,
it's already stale; we'd care about core.abbrev, for
instance, when %(objectname:short) is used.
Signed-off-by: NJeff King <peff@peff.net>
Signed-off-by: NJunio C Hamano <gitster@pobox.com>