for conditional storing and quick resynchronisation (not sure if mail clients are actually using it that).
each message now has a "modseq". it is increased for each change. with
condstore, imap clients can request changes since a certain modseq. that
already allows quickly finding changes since a previous connection. condstore
also allows storing (e.g. setting new message flags) only when the modseq of a
message hasn't changed.
qresync should make it fast for clients to get a full list of changed messages
for a mailbox, including removals.
we now also keep basic metadata of messages that have been removed (expunged).
just enough (uid, modseq) to tell client that the messages have been removed.
this does mean we have to be careful when querying messages from the database.
we must now often filter the expunged messages out.
we also keep "createseq", the modseq when a message was created. this will be
useful for the jmap implementation.
renaming inbox is special. the mailbox isn't renamed, but its messages moved to
a new mailbox. we weren't updating the destination mailbox uidnext with the new
messages. the fix not only sets the uidnext correctly, but also renumbers the
uids, starting at 1.
this also adds a consistency check for message uids and mailbox uidnexts, and
for mailbox uidvalidity account nextuidvalidity in "mox verifydata".
this also adds command "mox fixuidmeta" (not listed) that fixes up mailbox uidnext
and account uidvalidity. and command "mox reassignuids" that will renumber the
uids for either one or all mailboxes in an account.
the backup command will make consistent snapshots of all the database files. i
had been copying the db files before, and it usually works. but if the file is
modified during the backup, it is inconsistent and is likely to generate errors
when reading (can be at any moment in the future, when reading some db page).
"mox backup" opens the database file and writes out a copy in a transaction.
it also duplicates the message files.
before doing a restore, you could run "mox verifydata" on the to-be-restored
"data" directory. it check the database files, and compares the message files
with the database.
the new "gentestdata" subcommand generates a basic "data" directory, with a
queue and a few accounts. we will use it in the future along with "verifydata"
to test upgrades from old version to the latest version. both when going to the
next version, and when skipping several versions. the script test-upgrades.sh
executes these tests and doesn't do anything at the moment, because no releases
have this subcommand yet.
inspired by a failed upgrade attempt of a pre-release version.
