Don't interfere with the notmuch unread tag.

[hlieberman]

Right now, afew tramples the notmuch unread tag, interfering with notmuch-el.

This patch will change that behavior to not modify the unread tag.

[wwentland]

This would be very useful to have. For now I am using the following to approximate this behaviour:

[Filter.0]
message = 'Retags all messages not tagged as junk or killed as inbox'
tags = +inbox;-new
tags_blacklist = killed;spam

[GuillaumeSeren]

Hey @hlieberman
I didn't notice this behaviour until reading your PR, to me it might more be something that the user can configure, than just changing the default for everybody.

[GuillaumeSeren]

Hey,
this is not moving and get no negative feedback, let's merge it.

[flokli]

This basically triggered #158.

[GuillaumeSeren]

@flokli Yes it is true,
if it is a problem we can revert it, but I've only tested them on python-2, now I'll test on both python-2 and python-3 🤖