[geary] (6 commits) Non-fast-forward update to branch wip/713530-background-sync

[Michael Gratton <mjog src gnome org>]

The branch 'wip/713530-background-sync' was changed in a way that was not a fast-forward update.
NOTE: This may cause problems for people pulling from the branch. For more information,
please see:

 https://wiki.gnome.org/Git/Help/NonFastForward

Commits removed from the branch:

  7aedb49... Ensure initial sync has an accurate idea of mailbox message
  b8d4c91... Ensure the account synchroniser actually does some vector e
  bfd9a73... Ensure duplicate messages are still added to local folders.
  63ff253... Add some debugging so we know when a background sync has co
  d124c07... Enforce a an API contract clause for Geary.Folder.list_emai

Commits added to the branch:

  5387bd8... Don't use local/remote counts to determine if folder should
  b96888e... Ensure the account synchroniser actually does some vector e
  b33e306... Ensure duplicate messages are still added to local folders.
  5ccc88f... Add some debugging so we know when a background sync has co
  8f90cf1... Enforce a an API contract clause for Geary.Folder.list_emai
  c4559f6... Only prefetch messages that have not been seen before.