Currently, a line is interpreted to be a trailer line if it contains a
separator. Make parsing stricter by requiring the text on the left of
the separator, if not the empty string, to be of the "<token><optional
whitespace>" form.
Signed-off-by: Jonathan Tan <jonathantanmy@google.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>