ref-filter: convert email atom parser to use err_bad_arg()

The error message for a bogus argument to %(authoremail), etc, is: $ git for-each-ref --format='%(authoremail:foo)' fatal: unrecognized email option: foo Saying just "email" is a little vague; most of the other atom parsers would use the full name "%(authoremail)", but we can't do that here because the same function also handles %(taggeremail), etc. Until recently, passing atom->name was a bad idea, because it erroneously included the arguments in the atom name. But since the previous commit taught err_bad_arg() to handle this, we can now do so and get: fatal: unrecognized %(authoremail) argument: foo which is consistent with other atoms. Signed-off-by: Jeff King <peff@peff.net> Acked-by: Taylor Blau <me@ttaylorr.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>