[dovecot/core] 90355e: imapc: Added support for imapc_features=modseq

[GitHub]

  Branch: refs/heads/master
  Home:   https://github.com/dovecot/core
  Commit: 90355e35d1139e446a99733986a9181bd7f05dd4
      https://github.com/dovecot/core/commit/90355e35d1139e446a99733986a9181bd7f05dd4
  Author: Timo Sirainen <timo.sirainen at dovecot.fi>
  Date:   2016-04-23 (Sat, 23 Apr 2016)

  Changed paths:
    M src/lib-storage/index/imapc/imapc-mail.c
    M src/lib-storage/index/imapc/imapc-mailbox.c
    M src/lib-storage/index/imapc/imapc-settings.c
    M src/lib-storage/index/imapc/imapc-settings.h
    M src/lib-storage/index/imapc/imapc-storage.c
    M src/lib-storage/index/imapc/imapc-storage.h
    M src/lib-storage/index/imapc/imapc-sync.c

  Log Message:
  -----------
  imapc: Added support for imapc_features=modseq

If the remote server supports CONDSTORE or QRESYNC extensions we'll use the
remote's MODSEQ and HIGHESTMODSEQ counts.

There are some situations where the HIGHESTMODSEQ isn't updated exactly
correctly on an open mailbox, so this feature shouldn't be fully relied on.
It was primarily implemented for dsync+imapc support - both for preserving
modseqs and also for HIGHESTMODSEQ lookups.