Refactor the package comparison user interface

Considering the amount of data that needs to be processed for this, we need to simplify the initial display of data.

So i feel that the initial compare should just be a list of eligible platforms, with a link (either a real page or an ajax call of some sort) to display the comparison between just the current and target platforms.

i think i can also improve the performance of this screen by offloading more to the database layer.

during evaluation i intend to create 2 temporary tables, one with the denormalized form of the current packages the other with the denormaized form of the target platform.

Creating the temporary tables should be pretty inexpensive and it allows us to more easily detect differences between the package sets with a simple join between the two temporary tables rather than having to iterate through every package on every platform.

The only problem comes in with the 'version' string, which needs to be normalized better to create an efficient query.

I think that is something that should perhaps be offloaded to the verify task, so that instead of trying to compare two strings we are comparing the values of the different components.

looking at it a bit more, im considering processing the version strings into a single integer that can be compared.

this integer would be relatively large, but it would still be easier to compare than a string or several different columns.
it could work provided none of the version numbers go over 99 (or perhaps it should be 3 digits?)

6.x-2.1-alpha3 turns into 6|00|02|01|01|03

6.12 is 6|12|00|00|04|00

HEAD is (of course) 0

it makes it easy to detect that 7.x-3.0-alpha4 (70003000104) is newer than 6.x-2.0-beta1 (60002000201)

The query would then just be finding the items in the current temporary table that have a lower version or schema version than the target platform.

Got the code almost done. it's pretty damn fast now, but i should still add some indexes

here's the new interface, i'm still adding in the package comparison table.

This is almost ready, apart from some small user interface issues, the form is a lot simpler now.

i'm thinking perhaps we should add a dependency to jquery ui for this, as the compare packages screen should really be a modal dialog that is opened up. (http://jqueryui.com/demos/dialog/modal-message.html)

also the accordion widget would work very will with the site creation form. (http://jqueryui.com/demos/accordion/)

i forgot to mention that you need to run update.php, as this adds a new column

The no upgrades available issue is likely related to : http://drupal.org/node/584188

if you revert the patch, you will see that the old form won't let you migrate either.

I committed this.

any additional issues with this form (and there are probably several) should get new issues created for them.

It could use some more testing, to make sure everything is working correctly.

It also needs some spit and polish on the interface level.

any minor (or major) issues you can find will help.