Sashiko email policy precedence

["Danilo Krummrich" <dakr@kernel.org>]

Hi Roman,

We just enabled nova-gpu with the reply_all email policy and I noticed that
sashiko does not actually send any such replies.

I did dig a bit and it seems that the logic here is that if there is another
mailing list Cc'd that is in the sashiko email policy, but does not have
reply_all set, reply_all is removed (while reply_to_author is always honored
regardless).

In contrast, if another list that does not have an email policy at all is Cc'd,
reply_all is not removed.

For nova-gpu that means that the only way currently to get the reply_all policy
would be to never Cc the rust-for-linux list (which only sets reply_to_author)
in the first place.

In fact, it seems to boil down to any subsystem list that handles Rust code is
stuck with reply_to_author, regardless whether it wants more (e.g. reply_all) or
less (no reply_to_author).

Given that the rust-for-linux list is like the lkml, I think we should special
case it, so it does not mess with the policy from other subsystems too much.

One low-hanging fruit to improve this a bit would of course be to add
cc=nova-gpu, but I'd still prefer to be able to get reply_all without dropping
the rust-for-linux list.

Maybe adding a separate flag to be set by "catch all" mailing lists could be an
option?

E.g. when 'passive=true' is set and a passive list is matched with a non-passive
one the passive one won't impose its restrictive defaults (e.g.
reply_all=false) on the non-passive one.

- Danilo