Automatic suppression of non-duplicate messages

[Eirik Byrkjeflot Anonsen <eirik@eirikba.org>]

As has been mentioned a few times before, notmuch chooses to silently
drop any message that has the same message-id as an already-seen
message.

In another thread, Austin Clements said:

> notmuch tracks all copies of a message, but its output generally shows
> messages, rather than files, so you see a message only once regardless
> of how many copies there are in the file system.

That's not what I see.  If I search for a term that only appears in one
of the "copies", none of the copies are included in the search result.

This is with:
$ dpkg -l | grep notmuch | <remove uninteresting stuff>
ii  libnotmuch3                                    0.13.2-1
ii  notmuch                                        0.13.2-1
ii  notmuch-emacs                                  0.13.2-1


However, I still find it a much bigger problem that notmuch will
silently and automatically discard new mail without letting me know that
they exist, let alone allow me to read them.  (I.e. when receiving a new
mail that happens to have the same message-id as a previously received
mail.)

Personally, I find almost no cost in seeing all near-duplicates of the
same message (a cost that could be further mitigated by clever
presentation).  Conversely, I find a huge cost in never seeing some
messages at all.

This is currently the main issue that keeps me from switching to
notmuch.  (Importing my mail into notmuch dropped roughly 6800 mails.
I'm sure most of these mails are near-duplicates, but I've found 34
mails so far that are emphatically not.)

I think it is a nice and useful design to use the message-id as the
unique id to refer to a specific message.  Most of the time, this will
work just fine.  However, it is less useful to blindly trust that this
will always work correctly.

eirik