folded headers

[Harry Putnam]

I see some headers in mail that are multiple lines.
Is that something gnus does or something else in the mail chain?

Is there some format involved that will be recognized by mail clients
as multiple line?

How can I do that manually... like in a script that parses incoming
mail?

I get mail to root from gentoo linuxs' emerge command that outputs a
totally non-informative subject line:

  Subject: [portage] ebuild log for multiple packages [...]

In the body of that mail will be lines like this:

  - sys-fs/udev-130-r1
  - sys-fs/device-mapper-1.02.28
  - media-libs/tiff-3.8.2-r5
  - sys-apps/pciutils-3.0.2
  - app-admin/eselect-emacs-1.5-r1
  - sys-auth/pambase-20081028-r1
  - sys-kernel/linux-headers-2.6.27-r2

Either inside gnus or through procmail, I want to fold those lines
into the subject line, in a way that mailclients will recognize.  Not
all on one line.

I can script it any way required but want to know if there is a format
involved to get those folded style headers.. or if gnus is the one
doing the folding.. then how to do it inside of gnus.