[Dovecot] using dsync to convert mailboxes looses caching options

[Timo Sirainen]

On Thu, 2011-12-08 at 09:19 +0000, Mark Zealey wrote:
> OK now it's copying the timestamp fields for tmp ones. However:
> 
> 1) hdr.* fields are not being copied at all (unlike in previous releases)

They are in my tests.. This also happens if the destination doesn't
exist?

> 2) although the decisions are now being recorded; the items are not actually being put into the cache for previously sync'd mails. New mails are having all the cache information produced however.

This is intentional. Doing anything else would be horribly inefficient.
Note that dsync isn't *copying* cached data. It's simply setting the
caching decisions, and the mail saving code parses the mails and updates
cache.

> Perhaps this should be activated by a new option to dsync; if people are using this for backup (rather than conversion) caches could get relatively large?

Hm. Maybe..