[geary] (5 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:

  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.

Commits added to the branch:

  8db48f8... Ensure the account synchroniser actually does some vector e
  a74dfb5... Ensure duplicate messages are still added to local folders.
  f55cdc3... Add some debugging so we know when a background sync has co
  926aae4... Enforce a an API contract clause for Geary.Folder.list_emai
  7c5d89b... Only prefetch messages that have not been seen before.