when syncing flags but not re-newing non-fetched messages, there is no
need to query the message size for all messages, as the old ones are
queried only for their flags.
that's what the sources already assumed anyway. size_t is total
overkill, as No Email Ever (TM) will exceed 2GiB.
this also fixes a harmless format string warning in 32 bit builds.
that pattern may very well expand to INBOXNOT, which would naturally
live under Path, so we need to look into the Path. of course, this
actually makes sense only if there *is* a Path, and complaining about
it being absent is backwards.
in the case of imap stores, the failure is bound to the server config,
not just the store config.
that means that the storage of the failure state needs to be private to
the driver, accessible only through a function.
propagating many messages from a fast store (typically maildir or a
local IMAP server) to a slow asynchronous store could cause gigabytes of
data being buffered. avoid this by throttling fetches if the target
context reports memory usage above a configurable limit.
REFMAIL: 9737edb14457c71af4ed156c1be0ae59@mpcjanssen.nl
don't retry dead Stores for every Channel.
this also introduces a state for transient errors (specifically, connect
failures), but this is currently unused.
the seznam.cz IMAP server seems very eager to send UIDNEXT responses
despite not supporting UIDPLUS. this doesn't appear to be a particularly
sensible combination, but it's valid nonetheless.
however, that means that we need to save the UIDNEXT value before we
start storing messages, lest imap_find_new_msgs() will simply overlook
them. we do that outside the driver, in an already present field - this
actually makes the main path more consistent with the journal recovery
path.
analysis by Tomas Tintera <trosos@seznam.cz>.
REFMAIL: 20141220215032.GA10115@kyvadlo.trosos.seznam.cz
