The UI for upgrades to Drupal 8 from Drupal 6/7 is being developed in contrib, to be pulled into core when "ready" (the current hope is to get it in for RC1). This UI is under development as migrate_upgrade.
The detailed current design plan is in a Google doc - anyone can read and comment there. Broadly, the workflow should be as follows:
- Overview page (at http://example.com/upgrade), describing what is to happen and how to prepare for it.
- Credentials page - get the DB info for the source site, as well as the address from which to fetch the files.
- Report/confirmation page - After analyzing the source database, report on specifically what is going to happen - what source modules will be imported into what destination modules, and what source modules are not being upgraded.
- Batch - the migrations are run through the normal Batch API.
- Post-upgrade report - message summarizing successful/failed migrations, with link to watchdog listing of specific messages.
When returning to /upgrade, the following workflow will happen:
- Overview page - reports that an upgrade has already been performed, and offers the option of rolling back and starting over, or running an incremental upgrade (importing new content, and content that now has an upgrade path which previously didn't).
- If rolling back was chosen, imported configuration entities (e.g., fields, node types, etc.) and content are deleted and migration configuration removed (simple configuration is *not* restored to its original state), and we return to the original overview page.
- Otherwise, we skip the credentials page (we already have that information) and go directly to the report/confirmation page, proceeding normally from there.