[MERGE] Content filtering (EOL part 2 of 3)

[Martin Pool]

On Fri, Jul 18, 2008 at 11:22 PM, Robert Collins
<robertc at robertcollins.net> wrote:
>> I don't agree however that this mechanism needs to land in order
>> for us to land content filtering. To begin with, no plugin using
>> content filtering will even load on versions of Bazaar without
>> content filtering in the core - the registration API will be
>> absent.
>
> I agree that that mechanism can likely be deferred. (Not an unqualified
> agreement - devil in the details). However, something to prevent old
> bzr's even _looking_ at a content-filtered tree is IMO very important.

If someone uses an old bzr to look at a tree that has had content
filtering applied they will just not see the filtering applied when
they do diff, etc.  This should be reasonably understandable.

If we wanted watertight protection against people even looking at a
content-filtered tree we'd need not just a new workingtree format but
also a new repository format to say that trees in here might have
filtering information.  I think this is too heavyweight.  With the
infrastructure we have at the moment although users can go through
upgrades there is some hassle.

I think we have already talked about this and I'd like to just go
ahead as it is.

In future perhaps we need an alternative mechanism to format markers,
which would allow us to mark that a particular bzr version or
capability is needed, without making the user upgrade before they can
use that feature.  Perhaps this is equivalent to adding a new format
and automatically upgrading when needed.

-- 
Martin <http://launchpad.net/~mbp/>