I would like to confirm my understanding of what will happen in the trunk
update stream as we make the transition to Spur image format in Squeak 5.0.

We currently have the trunk update stream, which is governed by update maps
called 'update' in the source.squeak.org/trunk repository. This update
stream is applicable to Squeak images up to the initial release of the
Squeak 4.6 image. These are images in the non-Spur image formats (6504
or 6505 for 32-bit images, and 68002 for a 64-bit image).

During the development period leading up to Squeak 5.0, which uses the
new Spur image (format number 6521 for the 32-bit Spur image), the
update stream has been governed by update maps called 'update.spur' in
source.squeak.org/trunk.

For Squeak 5.0, the update stream will continue to be governed by update
maps called 'update' in the source.squeak.org/trunk repository. Users of
Squeak 5.0 will see a normal trunk update stream from that point forward,
and will now be using the Spur image format.

For Squeak 4.6, the update stream will continue to be called 'update',
but will now be in the source.squeak.org/squeak46 repository. These update
maps are not yet in the squeak46 repository, but will be added as required.
The Squeak 4.6 release image points to this update stream. An effort will
be made to keep the squeak46 update stream in sync with trunk through the
next Squeak release cycle.

For an existing trunk image, such as a Squeak 4.5 image that has been kept
up to date with the trunk, it will be necessary to switch from
source.squeak.org/trunk with update map name 'update', to a new setting
of source.squeak.org/squeak46 with update map name 'update', This change
must be made more or less concurrently with the Squeak 5.0 release.

Questions:

1) Is the above summary correct?

2) Is it possible for the trunk update stream to force an existing trunk
image (originating from Squeak 4.5 or earlier) to switch over to the squeak46
repository automatically, such that updates can proceed without loading
Spur-specific changes into a non-Spur trunk image?

3) Previously, the release-specific repository (e.g. source.squeak.org/squeak45
for Squeak 4.5) was used for applying a few important fixes to a stable
release. Assuming that this is also the intent for Squeak 4.6, and that we
also want to make an effort to permit non-Spur images to stay in sync with
trunk for some period of time (nominally one release cycle), then would it
be helpful to consider providing a trunk-compatible update stream for non-Spur
images during the transition period? I am not sure how that should work
(possibly something involving an 'update.classic' update map), but I would
like to know if conceptually it is something we should be trying to do.

Thanks,
Dave