bug#17845: 24.2; nnimap performs 'intial sync' on all mailboxes every time 'M-x gnus' is run

[Duncan Bayne]

I'm using nnimap, configured to use the Fastmail IMAP servers.  Every
time I do 'M-x gnus', nnimap performs an 'initial sync' of each mailbox,
downloading many MiB of data.

In addition to being very slow, this is probably irritating the folks at
Fastmail no end.

My gnus configuration is as follows:

;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
(require 'gnus)

(setq user-mail-address "duncan@bayne.id.au")
(setq user-full-name "Duncan Bayne")

(setq gnus-select-method
      '(nnimap "duncan@bayne.id.au"
               (nnimap-address "mail.messagingengine.com")
               (nnimap-server-port 993)
               (nnimap-stream ssl)
               (nnimap-list-pattern ("INBOX" "INBOX.*"))))

(setq message-send-mail-function 'smtpmail-send-it
      smtpmail-starttls-credentials '(("mail.messagingengine.com" 587 nil nil))
      smtpmail-auth-credentials '(("mail.messagingengine.com" 587 
"duncan@bayne.id.au" nil))
      smtpmail-default-smtp-server "mail.messagingengine.com"
      smtpmail-smtp-server "mail.messagingengine.com"
      smtpmail-smtp-service 587
      gnus-ignored-newsgroups "^to\\.\\|^[0-9. ]+\\(\\|$\\)\\|^[\"]\"[#'()]")

(defun my-message-mode-setup ()
  (setq fill-column 72)
  (turn-on-auto-fill))
(add-hook 'message-mode-hook 'my-message-mode-setup)
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;

In GNU Emacs 24.2.1 (x86_64-unknown-linux-gnu, GTK+ Version 2.24.20)
 of 2014-02-27 on duncan-laptop
Windowing system distributor `The X.Org Foundation', version 11.0.11405000
Important settings:
  value of $LC_ALL: nil
  value of $LC_COLLATE: nil
  value of $LC_CTYPE: nil
  value of $LC_MESSAGES: nil
  value of $LC_MONETARY: nil
  value of $LC_NUMERIC: nil
  value of $LC_TIME: nil
  value of $LANG: en_AU.UTF-8
  value of $XMODIFIERS: nil
  locale-coding-system: utf-8-unix
  default enable-multibyte-characters: t

Major mode: Group

Minor modes in effect:
  gnus-undo-mode: t
  global-diff-hl-mode: t
  diff-auto-refine-mode: t
  global-auto-revert-mode: t
  global-undo-tree-mode: t
  undo-tree-mode: t
  global-hl-line-mode: t
  global-linum-mode: t
  linum-mode: t
  delete-selection-mode: t
  cua-mode: t
  tooltip-mode: t
  mouse-wheel-mode: t
  file-name-shadow-mode: t
  global-font-lock-mode: t
  font-lock-mode: t
  blink-cursor-mode: t
  auto-composition-mode: t
  auto-encryption-mode: t
  auto-compression-mode: t
  column-number-mode: t
  line-number-mode: t
  transient-mark-mode: t

Recent input:
M-x g n u s <return> n M-x r e p o <tab> r <tab> <
return>

Recent messages:
nnimap read 3065k from mail.messagingengine.com (initial sync of 30 groups; 
please wait)
nnimap read 3163k from mail.messagingengine.com (initial sync of 30 groups; 
please wait)
nnimap read 3331k from mail.messagingengine.com (initial sync of 30 groups; 
please wait)
nnimap read 3482k from mail.messagingengine.com (initial sync of 30 groups; 
please wait)
nnimap read 3622k from mail.messagingengine.com (initial sync of 30 groups; 
please wait)
nnimap read 3642k from mail.messagingengine.com (initial sync of 30 groups; 
please wait)
nnimap read 3761k from mail.messagingengine.com (initial sync of 30 groups; 
please wait)
Checking new news...done
Auto-saving...
Making completion list...

Load-path shadows:
~/.emacs.d/ruby-mode/ruby-mode hides 
/usr/local/share/emacs/24.2/lisp/progmodes/ruby-mode
~/.emacs.d/emms/tq hides /usr/local/share/emacs/24.2/lisp/emacs-lisp/tq

Features:
(shadow sort mail-extr emacsbug sendmail help-mode view nndraft nnmh
nnfolder utf-7 network-stream auth-source eieio starttls nnimap
parse-time tls utf7 netrc gnus-agent gnus-srvr gnus-score score-mode
nnvirtual gnus-msg gnus-art mm-uu mml2015 epg-config mm-view mml-smime
smime password-cache dig mailcap nntp gnus-cache gnus-sum nnoo
gnus-group gnus-undo nnmail mail-source gnus-start gnus-spec gnus-int
gnus-range message format-spec rfc822 mml mml-sec mm-decode mm-bodies
mm-encode mail-parse rfc2231 rfc2047 rfc2045 ietf-drums mailabbrev
gmm-utils mailheader gnus-win uniquify diff-hl face-remap vc-hg vc-git
cl-lib vc-dir ewoc vc ediff-merg ediff-diff ediff-wind ediff-help
ediff-util ediff-mult ediff-init ediff vc-dispatcher diff-mode geiser
emotion-iconous-mode xml jabber-autoloads gnus gnus-ems nnheader
gnus-util mail-utils mm-util mail-prsvr wid-edit ws-trim tomatinho
autorevert find-file-in-project ido undo-tree slime pp hyperspec
browse-url multi-term warnings advice advice-preload term disp-table
ehelp electric jka-compr-ccrypt jka-compr hl-line linum delsel cua-base
php-mode etags speedbar sb-image ezimage dframe assoc yaml-mode
feature-mode cucumber-mode sass-mode coffee-mode comint ansi-color ring
js2-mode cc-langs haml-mode help-fns js byte-opt bytecomp byte-compile
cconv macroexp json imenu newcomment cc-mode cc-fonts cc-guess cc-menus
cc-cmds cc-styles cc-align cc-engine cc-vars cc-defs markdown-mode
derived edmacro kmacro thingatpt noutline outline easy-mmode easymenu
css-mode ruby-mode regexp-opt cl duncans_emacs time-date tooltip
ediff-hook vc-hooks lisp-float-type mwheel x-win x-dnd tool-bar dnd
fontset image fringe lisp-mode register page menu-bar rfn-eshadow timer
select scroll-bar mouse jit-lock font-lock syntax facemenu font-core
frame cham georgian utf-8-lang misc-lang vietnamese tibetan thai
tai-viet lao korean japanese hebrew greek romanian slovak czech european
ethiopic indian cyrillic chinese case-table epa-hook jka-cmpr-hook help
simple abbrev minibuffer loaddefs button faces cus-face files
text-properties overlay sha1 md5 base64 format env code-pages mule
custom widget hashtable-print-readable backquote make-network-process
dynamic-setting system-font-setting font-render-setting move-toolbar gtk
x-toolkit x multi-tty emacs)