Per-account locking

[Daniel Shahaf]

Sebastian Spaeth wrote on Tue, Sep 20, 2011 at 19:04:26 +0200:
> On Mon, 19 Sep 2011 23:05:08 +0300, Daniel Shahaf wrote:
> > Have you considered stamping a format number somewhere in metadatadir,
> > and have offlineimap check that number before writing anything into that
> > dir?
> > 
> > At least that would prevent similar problems going forward (since old
> > versions would see a too-new format number and abort).
> 
> Yeah, that would certainly be a solution, althought the really old
> versions (that are stable in distros now) wouldn't know or care or check
> something like this.

We could change the naming scheme of directories under ~/.offlineimap/.
This will ensure that old versions don't stomp on new versions' metadata,
but I'm not sure whether it'll have any ill effects on old/stable versions.

> But I like the approach and will think if we
> shouldn't adopt it. A "minimum-version-required" field, so to
> say. (actually the sqlite cache database has a db-format version field).
> 

But people can switch between cache backends at will (AIUI), so we can't
use anything specific to the SQLite backend for this purpose.

At Subversion we bump the SQLite 'user_version' whenever we change the
DB schema in an compatible way.  We have separate format file guards
when the SQLite DB is just a component of something.

> Sebastian