passthrough mode, feature request

Hi.

I started using hascash quite recently and as it happens I already have
found one missing feature: passthrough mode. It is a mode of operation
found in the Bogofilter software. A programme in this mode acts as
a=C2=A0filter and inserts a header that holds information that can later =
be
used by an MDA (e.g. procmail). For example Bogofilter headers look like
these:

 X-Bogosity: Unsure, tests=3Dbogofilter, spamicity=3D0.887269, version=3D=
1.1.5
 X-Bogosity: Spam, tests=3Dbogofilter, spamicity=3D1.000000, version=3D1.=
1.5
 X-Bogosity: Ham, tests=3Dbogofilter, spamicity=3D0.157896, version=3D1.2=
.0

Hashcash could insert X-Hashcash-Info (e.g.) for every X-Hashcash
found. The header might contain

* actual number of bits "spent"

* "double spend" test results

* stamp's age (this is redundant but makes filtering with procmail
  easier)

* all the information from the X-Hashcash except the rand and counter
  fields

The difference between X-Hashcash and X-Hashcash-Info is that the latter
can be truested by MDA during classification as it is first removed by
hashcash and then created again.

--=20
Best regards,
=C5=81ukasz Stelmach