bug#21182: 25.0.50; gnus: every other unread message is marked as read on each nnimap group refresh

[Nix <nix@esperi.org.uk>]

I reported:

> This happened after my first Emacs update for nearly a year (a bit of a
> 'big bang'), so it could have come from almost any change to nnimap
> since September last year. I'll do a bisection and hunt for it.

The first bad commit is

commit 242354a23acf214ad06d4e3e7e5f5580c8b21d4a (HEAD, refs/bisect/bad)
Author: Trevor Murphy <trevor.m.murphy@gmail.com>
Date:   Mon Jan 26 07:56:37 2015 +0000

    lisp/gnus/nnimap.el Allow using the Google X-GM-LABELS, if present

and indeed reverting this causes the devastating automatically-mark-
every-other-item-as-read behaviour to go away. I am *not* using gmail,
but Beehive, so clearly this is negatively affecting other imap servers,
when it should obviously have no effect on them.

I'm frankly surprised a bug this serious has persisted for half a year.
It makes me wonder if I'm the only person using trunk Emacs with non-
Google imap servers, or if this is something specific to the (rare)
Beehive server.

Now, if you'll excuse me, I have a huge inbox full of
wrongly-marked-as-read messages to sort through :(

-- 
NULL && (void)