Text like "{foo}" triggers an AsciiDoc attribute; we have to
write "\{foo}" to suppress this. But when the "foo" is not a
syntactically valid attribute, we can skip the quoting. This
makes the source nicer to read, and looks better under
Asciidoctor. With AsciiDoc itself, this patch produces no
changes.
Signed-off-by: Jeff King <peff@peff.net> Signed-off-by: Junio C Hamano <gitster@pobox.com>